The films were deposited both on polished Si (100) and Si substrates with a 10:1 aspect ratio trench pattern, ~6 μm wide and ~60 μm deep. The 10 x 10 x 0.5 mm 3 and 100 x 10 x 0.5 mm 3 polished Si substrate pieces and 10 x 10 x 0.5 mm 3 Si substrates, patterned with 10:1 AR features were all cleaned using an ultrasonic bath, 3 min each in acetone and ethanol, and finally blow-dried with nitrogen gas. The substrates were loaded into the SiC coated graphite susceptor, which had a maximum substrate area of 30 x 100 mm. Then the reactor was pumped down, backfilled with H2, and heated to deposition temperatures with a 2000 sccm flow of H2 at 5 kPa regulated by a throttle valve on the process pump. The temperature was stabilized for 5 min at the deposition temperature prior to the deposition process. Then a 1 sccm flow of TEB, to give a partial pressure of 1.18 Pa, was added together with 100 sccm of Xe or Ar, giving a noble gas partial pressure of 18 Pa, to start the deposition. The total pressure was kept at 5 kPa for all depositions, resulting in a transitional flow with a Knudsen number of about 1 corresponding to the 10:1 aspect ratio microstructure. The susceptor temperature was monitored by a pyrometer (Heitronics) which was connected in loop with the temperature controller. A few depositions were carried out using lateral high-aspect ratio structures (Pillar-Hall 38 chips from Chipmetrics) as substrate. The top membranes of the chips were removed after the deposition using scotch-tape. The deposited films both inside and outside of the later high aspect ratio structure were characterized using X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). The chip was then broken perpendicular to the opening for cross-sectional analysis by SEM.