The kinetics of indium/amorphous-selenium multilayer thin film reactions

Abstract

The reaction kinetics in vapor-deposited indium/amorphous-selenium (a-Se) multilayer thin films were studied using differential scanning calorimetry (DSC), x-ray diffraction (XRD), and transmission electron microscopy (TEM). A number of reactions were observed upon heating with characteristic temperatures which were found to be independent of the multilayer modulation wavelength. The initial interface reaction between In and a-Se is the formation of an In 2 Se phase. Kinetic analyses of the In 2 Se formation process combined with TEM observations indicated that interface reaction is characterized by the two-dimensional growth of pre-existing In 2 Se regions formed during deposition to impingement in the plane of the original In͞a-Se interface. The change of the density of In 2 Se grains with temperature was analyzed in terms of the derived kinetic parameters, which is consistent with TEM observations and the heat release measurements.

Formation reactions of chalcopyrite compounds and the role of sodium doping

“…This agrees with the prediction from the effective heat of formation model without [4] and with consideration of Na [5] as well as with experiments on alternating multilayer thin films of In and Se [6]. a) In the In-Se system there are two possible consecutive reactions:…”

“…Without Na the former two have been observed to consecutively take place [6], because in this case all three reactions are exothermic [5]. However, under selenium deficiency and with Na the second reaction becomes endothermic, whereas the first and the third reaction remain exothermic [5].…”

Structural and electronic properties of amorphous and polycrystalline In2Se3 films

“…Subsequent anneals of the In/a-Se multilayers cause the In 4 Se 3 nuclei to grow and to react with Se to form InSe and finally In 2 Se 3 . 17 While there are important differences in crystallization kinetics between the multilayer foils and the present coevaporated films, it's quite likely that crystalline nuclei, possibly In 4 Se 3 , form during coevaporation of indium and selenium onto cold substrates. In TEM studies Bernède et al observed microcrystallites in cold-deposited coevaporated In-Se films of various compositions, and found that the density of crystallites increased with increasing In content.…”

“…17 In that case differential scanning calorimetry and TEM studies show that nuclei of an orthorhombic phase form at Se/In interfaces during the cold deposition. 17 Lu and co-workers identify this orthorhombic phase as In 2 Se, 17 but more recent work 7,30 says that the orthorhombic structure is In 4 Se 3 . Lu et al explain that the orthorhombic phase forms first since it has the highest effective heat of formation in the In-Se system.…”

Real-time studies of phase transformations in Cu–In–Se–S thin films—3: Selenization of Cu–In precursors

“…Depending on the Se/In ratio of the starting film, different intermediate phases and mechanisms were suggested [13,16,17]. For the H 2 Se selenization of In, the phase sequence In-In 2 Se-InSe-In 2 Se 3 was proposed [6].…”