, ▁printing ▁of ▁in ks ▁containing ▁nan op articles , ▁electro de position , ▁and ▁a ▁technique ▁inspired ▁by ▁wa fer - b ond ing . ▁ ▁S elen ization ▁▁ ▁The ▁Se ▁supply ▁and ▁s elen ization ▁environment ▁is ▁important ▁in ▁determ ining ▁the ▁properties ▁and ▁quality ▁of ▁the ▁film . ▁When ▁Se ▁is ▁supplied ▁in ▁the ▁gas ▁phase ▁( for ▁example ▁as ▁H 2 Se ▁or ▁element al ▁Se ) ▁at ▁high ▁temper atures , ▁the ▁Se ▁becomes ▁incorpor ated ▁into ▁the ▁film ▁by ▁absor ption ▁and ▁subsequent ▁diffusion . ▁During ▁this ▁step , ▁called ▁ch al c ogen ization , ▁complex ▁interactions ▁occur ▁to ▁form ▁a ▁ch al c ogen ide . ▁These ▁interactions ▁include ▁formation ▁of ▁Cu - In - G a ▁inter met all ic ▁allo ys , ▁formation ▁of ▁intermediate ▁metal - sel en ide ▁binary ▁comp ounds ▁and ▁phase ▁separation ▁of ▁various ▁sto ichi ometric ▁C IG S ▁comp ounds . ▁Because ▁of ▁the ▁variety ▁and ▁complexity ▁of ▁the ▁re actions , ▁the ▁properties ▁of ▁the ▁C IG S ▁film ▁are ▁difficult ▁to ▁control . ▁ ▁The ▁Se ▁source ▁affect s ▁the ▁resulting ▁film ▁properties . ▁H 2 Se ▁offers ▁the ▁fast est ▁Se ▁incorpor ation ▁into ▁the ▁absor ber ; ▁ 5 0 ▁at % ▁Se ▁can ▁be ▁achieved ▁in ▁C IG S ▁films ▁at ▁temper atures ▁as ▁low ▁as ▁ 4 0 0   ° C . ▁By ▁comparison , ▁element al ▁Se ▁only ▁ach ieves ▁full ▁incorpor ation ▁with ▁reaction ▁temper atures ▁above