A Letter to Steven Pinker (and Bill Gates, for that matter) About A Letter to Steven Pinker (and Bill Gates, for that matter) About Global Poverty Global Poverty

Jason Hickel email@example.com
University of London

A Letter to Steven Pinker (and Bill Gates, for that matter) About A Letter to Steven Pinker (and Bill Gates, for that matter) About Global Poverty Global Poverty
71310.25148/CRCP.7.1.008318Class, Race and Corporate Power Class, Race and Corporate Power Volume 7 Issue 1 Article 3 2019 Follow this and additional works at: https://digitalcommons.fiu.edu/classracecorporatepower Part of the Anthropology Commons Recommended Citation Recommended Citation Hickel, Jason (2019) "A Letter to Steven Pinker (and Bill Gates, for that matter) About Global Poverty," Class, Race and Corporate Power: Available at: https://digitalcommons.fiu.edu/classracecorporatepower/vol7/iss1/3 This work is brought to you for free and open access by the College of Arts, Sciences & Education at FIU Digital Commons. It has been accepted for inclusion in Class, Race and Corporate Power by an authorized administrator of FIU Digital Commons. For more information, please contact firstname.lastname@example.com.
A response to a letter regarding claims made in the Guardian about the global poverty narrative and printed with permission from Jason Hickel's blog from Feb. 9, 2019.

Dear Steven, I'm writing to respond to a letter you posted regarding claims I made in the Guardian about the global poverty narrative. I'm addressing you directly because I think it's preferable to engaging in back-channel debates, and because I'd like to invite you to respond to what follows. This is an important question and it demands serious, honest engagement.

The point of my piece was that the story of global poverty is more complex than you and Gates have been willing to acknowledge, and the data do not support your narrative about neoliberal globalization. Let me elaborate on my key points here, to clear up any confusion, while also addressing your specific comments.

First, the long-term poverty graph (1820-present) developed by Max Roser and recently tweeted by Bill Gates is misleading and has little empirical legitimacy. There are a few reasons for this. Real data on poverty has only been collected since 1981, by the World Bank. It is widely accepted among those who research global poverty that any data prior to 1981 is simply too sketchy to be useful, and going back to as early as 1820 is more or less meaningless. The data for 1820-1970 comes from a source (Bourguignon and Morrisson 2002) that draws on the Maddison database on world GDP. That data was never intended to assess poverty, but rather the distribution of GDPand that for only a limited range of countries. Data for the global South is particularly thin, and there is very little that exists for prior to 1900. The data is not robust enough to draw meaningful conclusions about what was happening to people's livelihoods during the colonial period.

It is important to recognise that the graph mixes two very different measures. The measure for 1820-1970 is based on estimates of GDP per capita, with only rough guesses about household share, and takes little if any account of the goods and resources that people may have acquired from their land, from trees, from forests, from rivers and the sea, and in the form of gifts from relatives. We might try to speculate about the share of GDP that the poorest people had, but that's very different from telling us anything very useful about poverty. By contrast, the World Bank's measure for 1981ff is based on surveys that seek to assess household income and, wherever possible, consumption of all non-monetary goods. These two disparate measures cannot be united into a single long-term trend, and cannot be used to draw confident conclusions. Roser's graph might make for nice social media, but it's not rooted in science.

In fact, uniting the two methodologies is misleading in both directions. (1) By using GDP per capita from 1820-1970 it likely understates the resources that households had at their disposal in comparison to the representation of the later period, and (2) By including total consumption from 1981ff it likely overstates people's "income" in comparison to the representation of the earlier period.

The only way to construct a legitimate long-term graph would be to use a single consistent indicator. While data on GDP per capita alone is not regarded as a robust way of assessing poverty, it is at least available (if too patchy to be useful) for the whole period. But in such a graph the falloff in poverty since 1981 would not be nearly as steep, as it would not count non-monetary transactions. Alternatively, we could wait until someone devises a reasonable method for measuring poverty in terms of household consumption since 1820. But in the meantime, I think it's wise to refrain from making claims about long-term poverty trends that lack empirical validity.

You say: "Hickel's picture of the past is a romantic fairy tale, devoid of citations or evidence." On the contrary, as the above makes clear, it is the graph of the past on which you so glibly rely that is devoid of meaningful evidence.

As to my actual claims about the past, my argument was straightforward. I simply pointed out that we cannot ignore the fact that the period 1820 to circa 1950 was one of violent dispossession across much of the global South. If you have read any colonial history, you will know colonizers had immense difficulty getting people to work on their mines and plantations. As it turns out, people tended to prefer their subsistence lifestyles, and wages were not high enough to induce them to leave. Colonizers had to coerce people into the labour market: imposing taxes, enclosing commons and constraining access to food, or just outright forcing people off their land. The process of forcibly integrating colonized peoples into the capitalist labour system caused widespread dislocation (a history I cover in The Divide). Remember, this is the period of the Belgian labour system in the Congo, which so upended local economies that 10 million people diedhalf the population. This is the period of the Natives Land Act in South Africa, which dispossessed the country's black population of 90% of the country. This is the period of the famines in India, where 30 million died needlessly as a result of policies the British imposed on Indian agriculture. This is the period of the Opium Wars in China and the unequal treaties that immiserated the population. And don't forget: all of this was conducted in the name of the "free market".

All of this violence, and much more, gets elided in your narrative and repackaged as a happy story of progress. And you say I'm the one possessed of romantic fairy tales. The Maddison database on which you rely might tell us what the dispossessed gained in GDP per capita (eventually), but it does not tell us whether those gains offset their loss of lands, commons, supportive communities, stable local economies. And it tells us nothing about what global South economies might be like today had they been free to industrialize on their own terms (take the case of India, for instance).

Let me be clear: this is not a critique of industrialization as such. It is a critique of how industrialization was carried out during the period in question. If people had willingly opted into the capitalist labour system, while retaining rights to their commons and while gaining a fair share of the yields they produced, we would have a very different story on our hands. So let's celebrate what industrialization has achievedabsolutelybut place it in proper context: colonization, violence, dispossession and all. All we gain from ignoring this history is ignorance. Now, to the present period.

You say that the "massive fall of global extreme poverty" is simply a neutral fact of the data. But here again the data on this is more complex than you have ever acknowledged (I collaborated with Charles Kenny to review the basics here). The narrative that you and Gates peddle relies on a poverty line of $1.90 per day. You are aware, I'm sure, that this line is not a neutral phenomenon, handed down by the gods or given in nature. It was invented by people, is used for particular ends, and is hotly contested both inside and outside of academia. Most scholars regard $1.90 as far too low to be meaningful, for reasons I have outlined in my work many times (see here and here). See Reddy and Lahoti's withering critique of the $1.90 methodology here.

Here are a few points to keep in mind. Using the $1.90 line shows that only 700 million people live in poverty. But note that the UN's FAO says that 815 million people do not have enough calories to sustain even "minimal" human activity. 1.5 billion are food insecure, and do not have enough calories to sustain "normal" human activity. And 2.1 billion suffer from malnutrition. How can there be fewer poor people than hungry and malnourished people? If $1.90 is inadequate to achieve basic nutrition and sustain normal human activity, then it's too lowperiod. It's time for you and Gates to stop using it. Lifting people above this line doesn't mean lifting them out of poverty, "extreme" or otherwise.

Remember: $1.90 is the equivalent of what that amount of money could buy in the US in 2011. The economist David Woodward once calculated that to live at this level (in an earlier base year) would be like 35 people trying to survive in Britain "on a single minimum wage, with no benefits of any kind, no gifts, borrowing, scavenging, begging or savings to draw on (since these are all included as 'income' in poverty calculations)." That goes beyond any definition of "extreme". It is patently absurd. It is an insult to humanity.

In fact, even the World Bank has repeatedly stated that the line is too low to be used in any but the poorest countries, and should not be used to inform policy. In response to the Atkinson Report on Global Poverty, they created updated poverty lines for lower middle income ($3.20/day) and upper middle income ($5.50/day) countries. At those lines, some 2.4 billion people are in poverty todaymore than three times higher than you would have people believe. But even these figures are not good enough. The USDA states that about $6.7/day is necessary for achieving basic nutrition. Peter Edwards argues that people need about $7.40 if they are to achieve normal human life expectancy. The New Economics Foundation concludes that around $8 is necessary to reduce infant mortality by a meaningful margin. Lant Pritchett and Charles Kenny have argued that since the poverty line is based on purchasing power in the US, then it should be linked to the US poverty lineso around $15/day. The literature on this issue is now vast and nuanced -I have only scratched the surface hereand yet you pretend it doesn't even exist. That is intellectually irresponsible, and an inadequate approach to scholarship. You say: "The level at which one sets an arbitrary cutoff like 'the poverty line' is irrelevantthe entire distribution has shifted, so the trend is the same wherever you set it." Not so fast. In fact, the story changes quite a bit -and you know it. If we use $7.40 per day, we see a decline in the proportion of people living in poverty, but it's not nearly as dramatic as your rosy narrative would have it. In 1981 a staggering 71% lived in poverty. Today it hovers at 58% (for 2013, the most recent data). Suddenly your grand story of progress seems tepid, mediocre, and -in a world that's as fabulously rich as ourscompletely obscene. There is nothing worth celebrating about a world where inequality is so extreme that 58% of people are in poverty, while a few dozen billionaires have more than all of their wealth combined.

That's proportions. Don't get me wrong: proportions are an important indicatorand we should pay attention to it. But absolute numbers are equally important. In fact, that is the metric that the world's governments first agreed to target in the Rome Declaration in 1996, the precursor to the Millennial Development Goals. The goalposts were shifted to proportions in the following years, which created the impression of faster progress. But really now it's a moot point: if the goal is to end poverty, what matters is absolute numbers. Certainly that's what matters from the perspective of poor people themselves.

And if we look at absolute numbers, the trend changes completely. The poverty rate has worsened dramatically since 1981, from 3.2 billion to 4.2 billion, according to World Bank data. Six times higher than you would have people believe. That's not progress in my bookthat's a disgrace. It is a crushing indictment of our global economic system, which is clearly failing the majority of humanity. Your claims about global poverty intentionally skate around this fact. Again, that is not responsible scholarship.

But what's really at stake here for you, as your letter reveals, is the free-market narrative that you have constructed. Your argument is that neoliberal capitalism is responsible for driving the most substantial gains against poverty. This claim is intellectually dishonest, and unsupported by facts. Here's why:

The vast majority of gains against poverty have happened in one region: East Asia. As it happens, the economic success of China and the East Asian tigersas scholars like Ha-Joon Chang and Robert Wade have long pointed outis due not to the neoliberal markets that you espouse but rather state-led industrial policy, protectionism and regulation (the same measures that Western nations used to such great effect during their own period of industrial consolidation). They liberalized, to be surebut they did so gradually and on their own terms. Not so for the rest of the global South. Indeed, these policy options were systematically denied to them, and destroyed where they already existed. From 1980 to 2000, the IMF and World Bank imposed brutal structural adjustment programs that did exactly the opposite: slashing tariffs, subsidies, social spending and capital controls while reversing land reforms and privatizing public assetsall in the face of massive public resistance. During this period, the number of people in poverty outside China increased by 1.3 billion. In fact, even the proportion of people living in poverty (to use your preferred method) increased, from 62% to 68%. (For detailed economic data and references to the relevant literature, see Chapter 5 of The Divide).

In other words, the imposition of neoliberal capitalism from 1980 to 2000 made the poverty rate worse, not better.

Since 2000, the most impressive gains against poverty (outside of East Asia) have come from Latin America, according to the World Bank, coinciding with a series of left-wing or social democratic governments that came to power across the continent. Whatever one might say about these governments (I have my own critiques), this doesn't sit very well with your neoliberal narrative.

But there is something else that needs to be said here. You and Gates like to invoke the poverty numbers to make claims about the legitimacy of the existing global economic system. You say the system is working for the poor, so people should stop complaining about it.

When it comes to assessing such a claim, it's really neither absolute numbers nor proportions that matter. What matters, rather, is the extent of global poverty vis-à-vis our capacity to end it. As I have pointed out before, our capacity to end poverty (e.g., the cost of ending poverty as a proportion of the income of the non-poor) has increased many times faster than the proportional poverty rate has decreased (to use your preferred measure again). By this metric we are doing worse than ever before. Indeed, our civilization is regressing. Why? Because the vast majority of the yields of our global economy are being captured by the world's rich.

As I pointed out in the Guardian piece, only 5% of new income from global growth goes to the poorest 60% of humanitypeople living on less than $7.40/day. You have neither acknowledged this as a problem nor attempted to defend it. Instead you just ignore it, I suppose because it undermines your claims about how well the economy is working for poor people.

Here's how well it's working: on our existing trajectory, according to research published in the World Economic Review, it will take more than 100 years to end poverty at $1.90/day, and over 200 years to end it at $7.4/day. Let that sink in. And to get there with the existing systemin other words, without a fairer distribution of incomewe will have to grow the global economy to 175 times its present size. Even if such an outlandish feat were possible, it would drive climate change and ecological breakdown to the point of undermining any gains against poverty. It doesn't have to be this way, of course. We can end poverty right now simply by making the rules of our global economy fairer for the world's majority (I describe how we can do this in The Divide, looking at everything from wages to debt to trade). But that is an approach that you and Gates seem desperate to avoid, in favour of a blustering defense of the status quo.

You say, "The drastic decline in extreme poverty is corroborated by measures of well-being other than income that are correlated with prosperity, such as longevity, child mortality, maternal mortality, literacy, basic education, undernourishment, consumption, etc." Yes, life expectancy, mortality and education have improvedthis is fantastic news that we should celebrate! But, a few things:

(1) You can't make an argument about poverty by pointing to something else entirely. Consumption is increasing, yes. But that's not what's at stake here. What's at stake is whether consumption is increasing enough to raise people out of poverty.

(2) I'll be the first to agree that income and consumption are not the only measures of wellbeing. But one reason they are absolutely crucial is because they allow us to assess inequality in the distribution of world resources. A higher life expectancy among the poor is no justification for condemning them to a tiny and ever-shrinking share of global income. That is not a morally defensible position.

(3) In your work you have invoked gains in life expectancy and education as part of a narrative that seeks to justify neoliberal globalization. But here again that's intellectually dishonest. What contributes most to improvements in life expectancy is in fact simple public health interventions (sanitation, antibiotics, vaccines), and what matters for education is, well, public education. Indeed, the countries that have been most successful at this are those that have robust, free healthcare and education. Don't forget that the US has worse infant mortality than Cuba.

(4) As for hunger, your claim here relies on a methodology used by the FAO after 2012 that has been widely criticized by scholars. The hunger-reduction narrative depends on a calorie line that like your $1.90 poverty lineis too low to support normal human activity, ignores the impacts of food price crises, and tells us nothing about nutrient deficiencies. I cover this in detail in the second half of this paper. According to the FAO's earlier methodology, both the number and proportion of people in hunger was higher in 2009 than in 1995another trend that you glibly ignore.

In your concluding point, you descend to citing a piece by Ryan Bourne, not an academic who studies poverty but rather an employee of the Cato Institute, a right-wing think tank funded by the Koch Brothers. The piece is riddled with misleading claims which, when I pointed them out to him, he never corrected. I don't think we should consider this a valid source.

You opened your letter by slandering me as a "Marxist ideologue". I don't need to tell you that this doesn't count as an argument, and doesn't cover for the fact that you haven't addressed any of my substantive claims. In any case, I'm not quite sure what you mean. If by Marxist ideologue you mean someone who points out that the poverty data is more complex than your narrative allows, then, well, I suppose I am.

You ask for citations. Here are some you might try: Sven Beckert's Empire of Cotton, Ellen Wood's The Origins of Capitalism: A Longer View, Mike Davis' Late Victorian Holocausts, Adam Hochschild's King Leopold's Ghost, and of course Karl Polanyi's The Great Transformation.


Preparation of bismuth nanowire encased in quartz template for Hall measurements using focused ion beam processing

Masayuki Murata
Yasuhiro Hasegawa
Takashi Komine
Tomohiro Kobayashi
Preparation of bismuth nanowire encased in quartz template for Hall measurements using focused ion beam processing
N A N O E X P R E S SBismuth nanowireHall measurementfocused ion beamthermoelectrics PACS: 8107Gf
Forming electrodes on opposite sides of an individual bismuth nanowire was attempted to prepare for Hall measurements. Although a 1-mm-long bismuth nanowire which is completely covered with a quartz template has been successfully fabricated to prevent oxidation, it is very difficult to attach Hall electrodes on the opposite sides of the nanowire due to the quartz covering. One side of the cylindrical quartz template was removed by polishing without exposure of the nanowire to the atmosphere; the thickness between the polished template surface and the nanowire was estimated to be several micrometers. Focused ion beam processing was successfully employed to expose both surfaces of the nanowire under high vacuum by removing part of the quartz template. A carbon thin film was then deposited in situ on the wire surface to fabricate an electrical contact on the bismuth nanowire sample. Furthermore, the energy dispersive X-ray analysis was performed to the area processed by focused ion beam, and the bismuth component of the nanowire was successfully detected. It was confirmed that the focused ion beam processing was applicable to attach electrodes to bismuth nanowire for Hall measurement.

Background

Nanoscale structures such as superlattices and nanowires attract research interest due to their electrical transport properties. It has been expected that nanostructured thermoelectric materials would exhibit enhanced performance [1][2][3][4][5]. In particular, onedimensional bismuth nanowires have been expected to show an enhanced figure of merit as thermoelectric materials [2,3]. Bismuth, as a semimetal, has interesting electrical properties such as small effective mass, low carrier density, and a long mean free path; and the properties of bismuth, such as its Fermi surface and effective mass, have been well studied [6,7]. Bismuth nanowires have been fabricated using several methods for the study of the thermoelectric properties of one-dimensional systems [8][9][10][11][12][13]. Our group has fabricated a bismuth microwire array using a glass template and individual nanowires using a quartz template by application of a liquid-phase high pressure injection method [14][15][16][17][18][19][20][21][22][23][24]. The quartz template possesses an individual hole of several-hundred-nanometer diameter and over 1 mm long and is fabricated by identical procedure of an optical fiber for us to make the nanowire [21]. The simultaneous measurement of the Seebeck coefficient and resistivity was successfully achieved using the bismuth nanowire. The results implied that the carrier mobility of a nanowire less than 1 μm in diameter was significantly reduced compared with that for a bulk bismuth sample due to the collision at the quartz template surface, which functioned as a boundary condition, as a result of the classical size effect [25,26]. Although we have considered variations in the mobility of each carrier in the nanowire sample using a mean free path limitation model, direct measurement results have not yet been reported. Discussions have been based only on the model and temperature dependence measurement results of Seebeck coefficient and resistivity. Therefore, the carrier density and mobility should be evaluated by Hall measurement.

Bismuth nanowires are usually fabricated by using alumina templates [8][9][10][11]. Since bismuth nanowires are covered with the alumina template, the template must be removed so that the electrodes can be attached at the opposite sides of the nanowire for Hall measurements. Even if the alumina template component was completely removed using acid, it has been reported that the bare surface of the bismuth nanowire is likely to be oxidized in the atmosphere. Therefore, removal of the oxide layer covering the nanowire surface is a very important process to achieve ohmic contact with the electrodes [27][28][29]. Recently, a new fabrication process for bismuth nanowires called on-film formation of nanowires was reported [30], where the oxidized surface was removed by ion beam sputtering, and electrodes were deposited in situ on the bismuth nanowire without breaking the vacuum. However, a majority of the bismuth nanowire area was oxidized.

In the current research, however, the bismuth nanowires were covered with a quartz template; therefore, oxidation of the wire surface is prevented. Although such nanowire has apparent advantages, it was not considered to be suitable for the four-wire and Hall measurements because it is very difficult to remove the quartz component locally. However, in the previous study, we had successfully fabricated electrodes on the surface of the bismuth nanowire with ohmic contact using polishing and focused ion beam (FIB) processing and performed four-wire resistance measurement [31]. A local area of the bismuth wire was successfully exposed, and a carbon electrode was deposited on the bismuth wire in situ. In this paper, this method was applied for the preparation of a Hall measurement sample and discussed for a nanowire covered with a quartz template. The quartz template was cut using FIB processing to successfully expose the opposite side surfaces of a bismuth nanowire under high vacuum, and a carbon electrode was then immediately deposited on the surface of the bismuth nanowire.

Methods

An individual bismuth nanowire sample covered with a quartz template was prepared for the experiment. The diameter and length of the nanowire were ca. 700 nm and >1 mm, respectively. The individual nanowire was located in the center of the quartz template, of which the diameter was ca. 0.5 mm. The nanowire could be observed through the template using an optical microscope, due to the transparency of the template. However, removal of the quartz component was a significant challenge, even though the nanowire could be identified within the template. Several methods was attempted to achieve the removal of the template, with the conclusion that the quartz component would be best removed using polishing and FIB processing. The process used to fabricate the electrical contact on the bismuth nanowire is summarized in Figure 1. Firstly, a side of the quartz template was removed by polishing, as shown in Figure 1 (a). The typical diameter of the template was over 0.5 mm, which made the polishing process relatively easy using an optical microscope. Polishing was continued to achieve a distance of ca. 1 μm between the template surface and the bismuth nanowire. The roughness of the polished side surface was less than ± 50 nm. A thin film Pt-Pd layer (ca. 10 nm) was deposited on the polished surface to prevent charge up during the FIB process. The layer was completely removed by FIB processing after the fabrication of the electrodes was completed. The bismuth nanowire sample was installed into a dualbeam FIB apparatus capable of scanning ion microscopy (SIM) and scanning electron microscopy (SEM). The typical vacuum used for FIB processing was approximately 4.0 × 10 −5 Pa. During FIB processing, the position of the nanowire was not detected by SIM or SEM; however, the approximate position along the wire length was visualized using a position coordinate of the microscope. Gallium (Ga) ion beam sputtering was employed for FIB processing, with detection of the bismuth nanowire position, as shown in Figure 1 (b). The typical area of removed template was 3 × 10 μm, corresponding to the wire length direction and its perpendicular, respectively ( Figure 2a). A very slow sputtering rate was used for careful identification of the wire from SIM imaging. The SIM imaging could not directly detect the bismuth nanowire signal unless the wire was exposed using FIB processing. However, the use of an accelerated Ga ion beam (30 kV) made it possible to detect where the nanowire was lying, even if the wire was not completely exposed, and this was recognized under low vacuum SEM with application of a high voltage. Unfortunately, the acceleration voltage and angle of the SEM detector in the dual-beam FIB apparatus were not suitable to identify the wire position when covered with quartz. The high voltage energy Ga ion beam could penetrate the low density quartz template and could be detected at the bismuth nanowire surface. Therefore, the density difference was detected by SIM imaging, as shown in Figure 2a. The FIB processing was stopped right after the bismuth nanowire could be detected. The thickness between the surface of the template and the nanowire was estimated to be less than 500 nm. After successfully determining the position of the bismuth nanowire, rectangular portions of the template adjacent to the nanowire were removed by FIB to a depth of 5 μm from the quartz surface and a distance of 650 nm from the edge of bismuth nanowire (Figures 1 (c) and 2b). The template with bismuth nanowire was then tilted (ca. 60º) to expose each wire side for FIB processing, as shown in Figure 1 (d). A small area of the quartz wall (typically 1 × 1 μm) was exposed to the Ga ion beam (Figure 2c) and was gradually eliminated under low current. The structure was not observed even if the nanowire was located in there because the nanowire was packed into the quartz template. The FIB was stopped when any structure was identified, as shown in Figures 1 (e) and 2c. Figure 3 shows an SEM image of the exposed side of the wire in the quartz template after completion of the FIB processing. The inset of Figure 3 shows a magnified image after FIB processing, which shows the diameter of the FIB hole was less than 100 nm. Therefore, there is a possibility to apply this technique to nanowires with diameters less than 100 nm. The detected position of the bismuth nanowire was consistent with that expected in Figure 2a and with the estimated distance between the template surface and nanowire. Therefore, we could  conclude that this is a bismuth nanowire in the quartz template. Further processing was required at the opposite side (Figure 2d) to achieve a gap between both sides of the wire of typically <1 μm size, to enable taking Hall measurements with very small error. Inset of Figure 2d shows optical microscope image of the processed area. The nanowire could be observed through the quartz template. Thereby removal of the quartz component was successfully achieved using the FIB process without oxidation of the nanowire surface.

Results and discussion

It should be noted that there is a possibility that the bismuth component is vaporized when exposed to the Ga ion beam. Therefore, energy dispersive X-ray (EDX) analysis was performed at points 1 and 2 shown in Figure 3. Point 1 is the FIB-processed quartz template and is composed of Si and O as the main components of quartz, as shown in Figure 4. Although a Ga component was also observed due to the Ga ion beam processing, no bismuth component was detected at point 1. In contrast, at point 2 which was located in the center of the exposure area for the nanowire, the bismuth component was successfully detected (Figure 4). The electron beam for EDX has a typical spread of 1 × 1 μm; therefore, Si and O components were also detected at point 2. Al was also detected as a component of the microscope stage. The difference between points 1 and 2 indicates that the bismuth component remained after FIB processing.

Carbon electrodes were then deposited in situ on the exposed wire side surfaces to avoid oxidation and provide electrical contact points. Figure 5 shows a typical SEM image of carbon deposition on the exposed nanowire surface. The typical thickness of the carbon deposition was ca. 0.5 μm. After achieving the electrical contact, the carbon film layer was then extended to a copper electrode on the surface of the quartz template, as shown in Figure 1 (f ) and (g). The expected length of carbon between the surface of the bismuth nanowire and copper electrode is approximately 20 μm; therefore, the resistance of the carbon component was estimated to be ca. 200 Ω at an assumed resistivity of 50 μΩ m. The resistance would be reduced for a thicker carbon film. Figure 6 shows a schematic diagram of the configuration used for Hall measurements after polishing, FIB processing, and carbon deposition of the nanowire. The bismuth nanowire is fixed on an alumina plate as a back base prepared with copper electrodes. A thermometer is attached on the plate to measure the temperature. The thermocouple and heater are also attached in order to measure thermoelectromotive force for measurement of a Seebeck coefficient. The lead wires from the pad on the alumina plate are connected to the copper electrode located on the surface of the quartz template. The Hall effect signal in a magnetic field is measured using this configuration, which also makes it possible to perform resistance measurements by the four-probe method. The magnitude of the resistance using the two-probe method was relatively large due to the small diameter and long length of the nanowire. For example, the resistance of a bismuth nanowire with a diameter of 100 nm and a length of 1 mm was estimated to be ca. 166 kΩ for an assumed resistivity of 1.3 μΩm. The value is relatively large for the resistance measurements; therefore, the time constant of the circuit should be considered. If the four-probe method is used, then the resistance value can be easily controlled using a suitable gap for measurement of the voltage. Therefore, the configuration shown in Figure 6 enables the successful measurement of the electrical properties of nanowires, including not only the resistivity and Hall coefficient, but also the Seebeck and Nernst coefficients.  for a two-carrier model is expressed by
R H ¼ r H e pÀnb 2 pþnb ð Þ 2 , b ¼ μ n μ p ,
where r H is the Hall factor, n and p are the electron and hole carrier densities, respectively, and b is the mobility ratio between electrons μ n and holes μ p [32]. The value of r H is almost 1, even if carrier scattering processes are assumed. The values of n and p are taken from [7] for that of bulk Bi. The b value was estimated to be from 3 to 10, depending on the crystal orientation [33], and a value of b = 3 was selected as a severe assumption. The Hall resistance R Hall is approximately expressed as R Hall ¼ R H Bl S ¼ 4R H B πd , where d and B are the wire diameter and the magnitude of the magnetic field, respectively. Here the cross section of the nanowire (S) and the gap between metal electrodes for the Hall measurement (l) are approximated by S ¼ π d 2 À Á 2 and l ¼ d , respectively. Conditions of d = 100 to 1,000 nm were considered in B = 0.12 T, which satisfy the low magnetic field approximation at 300 K [34]. Therefore, the calculated |R Hall | is estimated to be from 0.19 Ω at 1,000 nm to 1.9 Ω at 100 nm. The electric current introduced into the bismuth nanowire for the measurement should ideally be less than 1 μA due to the small heat capacity of the narrow wire and the high resistance, so that an increase in temperature and burn out can be avoided. The absolute value of the measured Hall voltage was estimated to be 190 nV to 1.9 μV under the same conditions. Nanovolt-order voltage can be measured using a lock-in amplifier with modulation of the introduced current and magnetic field, which confirms that the configuration ( Figure 6) enables the experimental measurement of the Hall coefficient. The Hall coefficient of the bismuth nanowire enables us to evaluate carrier density and mobility experimentally. Therefore, the temperature dependence of resistivity of bismuth nanowires less than 1 μm can be described by the measurement of carrier density and mobility more directly than the calculation model of our previous study. In addition, it will be possible to measure not only Hall coefficient but also Nernst coefficient using the configuration; then, various electrical properties of bismuth nanowires can be evaluated.

Conclusions

A method to attach Hall electrodes on opposite sides of an individual bismuth nanowire encased in a quartz template was demonstrated using polishing, FIB processing, and carbon deposition. An accelerated Ga ion beam was used to detect the position of the nanowire in the quartz template without exposure. The quartz component covering the nanowire was then successfully removed with the Ga ion beam to locally expose the opposite side surfaces of the nanowire. Carbon thin films were then deposited in situ on the exposed wire surfaces to form electrical contacts, while avoiding oxidation of the nanowire. EDX analysis of the processed area indicated that the bismuth component remained after FIB processing.

The mobility reduction of bismuth nanowires less than 1 μm in diameter due to mean free path limitation at wire boundary will be evaluated experimentally by Hall measurement. Moreover, further investigations are planned using the configuration to examine the temperature and wire diameter dependence of the thermoelectric properties of bismuth nanowires, and the influence of the quantum effect using much smaller diameter of bismuth nanowires will be also estimated.

Figure 1
1Schematic diagram showing the processing for preparation of a bismuth nanowire for Hall measurements. (a) Polishing, (b) detection of the nanowire location, (c) removal of the side parts of the template, (d) exposure of the wire surface, (e) 3-D view of the exposed wire surface, (f) carbon deposition to form electrical contacts, and (g) contact between carbon film and copper electrodes located on the top of the quartz.

Figure 2
2SIM images during the FIB process. (a) Detection of the nanowire location, (b) removal of the side parts of the template, (c) side view tilted at 60º to expose the nanowire surface, and (d) top view of the processed area after FIB processing. Inset of (d) shows optical microscope image of the processed area.

Figure 3
3SEM image of the FIB processed area. The thick red line represents the location of the bismuth nanowire in the quartz template. The inset shows a magnified figure of the exposed side area of the nanowire. Points 1 and 2 indicate the locations used for EDX analysis.

Figure 4
4EDX spectra at points 1 and 2, as indicated inFigure 3.

Figure 5
5SEM image after carbon deposition onto the exposed side surface of the bismuth nanowire.The magnitudes of the Hall voltage measured for the nanowire are now discussed. The Hall coefficient (R H )

Figure 6
6Schematic diagram showing the configuration used for Hall measurement of the bismuth nanowire.
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Competing interestsThe authors declare that they have no competing interests.Authors' contributions MM carried out experiments, the polishing, FIB processing, EDX analysis, and drafted the manuscript. YH and TK guided the idea and the experiments and revised the manuscript. TK participated in the design of the FIB processing. All authors read and approved final manuscript.Authors' information MM is a PhD candidate under associate professor YH in the department of engineering, Saitama University, Japan.
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Preparation of bismuth nanowire encased in quartz template for Hall measurements using focused ion beam processing. Murata, Convenient online submission 7 Rigorous peer review 7 Immediate publication on acceptance 7 Open access: articles freely available online 7 High visibility within the fi eld 7. Cite this article as. Retaining the copyright to your article Submit your next manuscript at 7 springeropen.comCite this article as: Murata et al.: Preparation of bismuth nanowire encased in quartz template for Hall measurements using focused ion beam processing. Nanoscale Research Letters 2012 7:505. Submit your manuscript to a journal and benefi t from: 7 Convenient online submission 7 Rigorous peer review 7 Immediate publication on acceptance 7 Open access: articles freely available online 7 High visibility within the fi eld 7 Retaining the copyright to your article Submit your next manuscript at 7 springeropen.com