Growth of isolated and embedded Cu-containing chalcopyrite clusters and nanocrystals by dry processing

Abstract

A dry method for the growth of Cu-containing chalcopyrite nanocrystals on solid substrates is described. The experimental realization of the method relies on decoupling, by means of metal precursors, the two main issues of the growth of highly structured material: on the one hand, the structuring itself of the target material at the desired scale, and on the other hand, the actual chemical process ensuring the quality of the material. In the present approach, the precursors, consisting of species to be incorporated during the process in the final semiconducting compound, control the structuring, whereas chemical vapor deposition methods account for the chemistry of the process. The method proposed has been analyzed at a theoretical level by means of thermochemical calculations, which helped determine the ranges of interest of the experimental parameters involved in the deposition process. By choosing different distributions of Cu precursor deposited on standard glass substrates, nanocrystals, submicrometer polycrystalline dots, or macroscopic clusters of Cu-containing chalcopyrite compounds have been grown, either as isolated units or, alternatively, as embedded structures in a matrix of a binary chalcogenide compound, as a function of processing parameters. Compositional and structural analyses were used to determine the nature of the crystalline phases obtained thereof. Scanning probe techniques were used to characterize the samples at nanometer scale, demonstrating the suitability of the proposed method.

Formation of CuInS2–carbon multilayers in the spray ILGAR process

“…In the present paper, the formation process of these absorber films is discussed, which causes them to grow in multilayer stacks of nanometer‐scaled CIS layers. Recently, nanostructured chalcopyrite materials have attracted increasing interest since they may provide means to tailor the photovoltaic properties of these films 2, 3. Based on the present results, the spray ILGAR process may constitute a new and simple way of nanostructuring chalcopyrite materials.…”

“…The CIS top layer forms during the H 2 S post‐deposition annealing by the diffusion of indium into segregated Cu 2− x S agglomerates on the film surface. The indium diffusion starts upon the conversion of residual In 2 O 3 to In 2 S 3 by H 2 S 2, 5. The thickness of the CIS top layer can be varied approximately between 100 and 1000 nm by adjusting the [Cu]/[In] ratio of the spraying solution and the durations of the spraying and H 2 S steps in the ILGAR cycle, which determine the amount of In 2 O 3 present in the films prior to H 2 S post‐deposition annealing 2, 5.…”

“…The indium diffusion starts upon the conversion of residual In 2 O 3 to In 2 S 3 by H 2 S 2, 5. The thickness of the CIS top layer can be varied approximately between 100 and 1000 nm by adjusting the [Cu]/[In] ratio of the spraying solution and the durations of the spraying and H 2 S steps in the ILGAR cycle, which determine the amount of In 2 O 3 present in the films prior to H 2 S post‐deposition annealing 2, 5. In the present paper, the formation of the CIS multilayer structure in the lower part is investigated.…”

Optoelectronic evaluation of the nanostructuring approach to chalcopyrite-based intermediate band materials

“…Details on the growth system and procedures can be found in Ref. [6] and references therein. A triple-layer structure has been analyzed consisting of GaAs(substrate)/CuGaSe 2 / CuInSe 2 /CuGaSe 2 .…”

“…In particular, a suitable semiconductor matrix must have a larger bandgap than the nanostructured material, providing the confining potential energy barrier in the form of a suitable band offset. Procedures for the growth of chalcopyrite nanocrystals and mesoscopic clusters in the form of thin films have also been proposed that allow for the embedding step [6]. The embedding process of chalcopyrite nanocrystals into a barrier material, typically a related binary chalcogenide or a widegap ternary counterpart, can in principie be accomplished either during the growth of the nanostructured material itself or following a sequential process, like in the case of conventional quantum well structures.…”