Diffusion effects at the Au/p‐CuInSe₂ contact studied by XPS

Abstract

X‐ray excited photoelectron spectroscopy (XPS) was used to investigate the reactions at the interface between Au and CuInSe2 in case of Au/p‐CuInSe2 contacts produced by a procedure usually used to prepare low resistance ohmic contacts. Formation of an In‐Au alloy is observed after an annealing step at 300 °C in a nonoxidising atmosphere. Furthermore, it is found that some amount of gold diffuses into the CuInSe2 substrate. A tentative defect model is proposed to describe the formation mechanism of Au/ p‐CuInSe2 contacts.

Formation of Inert Bi2Se3(0001) Cleaved Surface

“…Outstanding chemical stability of cleaved Bi 2 Se 3 (0001) surface obtained in our experiment is in good relation with the general tendency known for many selenide crystals with layered structure. Low chemical reactivity in the air environment was earlier demonstrated for GaSe, InSe, In 4 Se 3 , TlGaSe 2 , and other layered selenides when the crystal surface was prepared by cleavage or special treatments to have a high surface structural quality. ,− Most interesting examples are the InSe and GaSe crystals where atomic layers are linked by weak van der Waals bonds similar with that of Bi 2 Se 3 and the Se-terminated optical surface can be formed by cleavage. ,,,− Cleaved (001) surface of InSe or GaSe is atomically flat and characterized by a very long living period in the air due to the absence of selenium dangling bonds. Respectively, for these crystals, the surface oxidation was detectable only after several months under ambient conditions. ,,, Surface oxidation of GaSe(001) starts by gallium oxide formation and appears to be controlled by defects at a cleaved surface. , We know from our own laboratory practice in GaSe nonlinear optical element handling that the low-defect GaSe crystals grown under an applied rotating heat field give a very stable cleaved surface.…”

Colloidal and Deposited Products of the Interaction of Tetrachloroauric Acid with Hydrogen Selenide and Hydrogen Sulfide in Aqueous Solutions

“…The findings, which seemingly disagree with an excess of chalcogens found with EDS and also with a higher volatility of sulfur as compared with selenium, can be rationalized in terms of surface decomposition of gold chalcogenides, and different lateral resolution and probing depths of the techniques. The assignment of the Au 4f components is not straightforward, particularly, since AuSe contains two sorts of Au atoms, the oxidation state of which is a matter of dispute [35][36][37][38][39][40][41][42][43][44][45]. The Au 4f 7/2 peaks at 84.0-84.4 eV reported for gold-gold selenide [39][40][41], gold-CdSe [44,45]), adlayers of Se or alkyl selenides at Au [45][46][47][48][49]59], etc., originate from Au 0 surfaces but not AuSe phases.…”

“…It is known from chemistry textbooks (for example [38]) that direct interaction between aqueous gold complexes and selenide ions results in precipitation of unstable gold selenides with unclear compositions. Preparation of nanoscale materials containing gold selenide have been described in a few publications [17,[39][40][41][42][43][44][45]. Nath and co-workers [39] have synthesized "AuSe nanoalloys" via fusion of elemental Au and Se nanoparticles in a micellar solution, typically with an excess of Au NPs.…”

“…Machogo et al [42] have recently reported the preparation of AuSe nanostructures mixed with metallic nanogold and unreacted Se by the reaction of HAuCl 3 ·3H 2 O with elemental Se in oleylamine. It has been found in several studies aimed at synthesis of hybrid nanostructures that gold commonly deposits onto metal selenide nanoparticles in elemental form [43][44][45]. Particularly, Cueva et al [45] have concluded from X-ray photoelectron spectroscopy (XPS) analysis that the shells deposited on CdSe NPs are most probably composed of AuSe or AuSeCl, which are instable and transform into dot-shaped Au 0 particles under the electron beam in Transmission electron microscopy (TEM).…”