Influence of deposition conditions on morphological, structural, optical and electro-physical properties of ZnSe films obtained by close-spaced vacuum sublimation

Effect of temperature and pH on structural, optical and electrical properties of Ni doped ZnSe nanoparticles

The mechanisms controlling the growth rate and composition of epitaxial CdTe and CdZnTe films were studied. The films were grown by isothermal closed space configuration technique. A GaAs 100 substrate was exposed sequentially to the elemental sources, Zn, Te, and Cd, in isothermal conditions. While growth of ZnTe followed an atomic layer epitaxy, ALE, regime self regulated at one monolayer per cycle; the CdTe films revealed different growth rates in dependence of the growth parameters,exposure and purge times. Combination of short purge times and larger Cd exposure times led to not self regulated growth regime for CdTe. This is ascribed to large Cd coverages that were dependent on Cd exposure times, following a Brunauer-Emmett and Teller-type adsorption. However, for longer purge times and or short Cd exposure times, an ALE self regulated regime was achieved with 2 ML per cycle. In this sense, the self-regulation of the growth is limited by desorption, instead of absorption, as in the traditional growth technique. Cd atoms substitution by Zn atoms and subsequent evaporation of surface Cd atoms during Zn exposure has been proved. The influence of these facts on the growth and composition of the alloy is discussed.

Adsorption, desorption, and interdiffusion in atomic layer epitaxy of CdTe and CdZnTe

Zinc selenide (ZnSe) thin films were deposited by RF magnetron sputtering in specific conditions, onto optical glass substrates, at different RF plasma power. The prepared ZnSe layers were afterwards subjected to a series of structural, morphological, optical and electrical characterizations. The obtained results pointed out the optimal sputtering conditions to obtain ZnSe films of excellent quality, especially in terms of better optical properties, lower superficial roughness, reduced micro-strain and a band gap value closer to the one reported for the ZnSe bulk semiconducting material. Electrical characterization were afterwards carried out by measuring the current–voltage (I-V) characteristics at room temperature, of prepared “sandwich”-like Au/ZnSe/Au structures. The analysis of I-V characteristics have shown that at low injection levels there is an Ohmic conduction, followed at high injection levels, after a well-defined transition voltage, by a Space Charge Limited Current (SCLC) in the presence of an exponential trap distribution in the band gap of the ZnSe thin films. The results obtained from all the characterization techniques presented, demonstrated thus the potential of ZnSe thin films sputtered under optimized RF plasma conditions, to be used as alternative environmentally-friendly Cd-free window layers within photovoltaic cells manufacturing.

Effect of RF Power on the Physical Properties of Sputtered ZnSe Nanostructured Thin Films for Photovoltaic Applications.

Transition metal chalcogenides have been one of the research hotspots in sodium-ion batteries (SIBs). In this work, Cu2Se-ZnSe heterojunction nanoparticles were embedded in carbon nanofibers to obtain the composites (Cu2Se-ZnSe-CNFs). As anodes for SIBs, Cu2Se-ZnSe-CNFs showed a reversible capacity of 310 mAh g−1 after 100 cycles at 0.1 A g−1. Their rate capacity is 237 mAh g−1 at 2 A g−1. The high specific capacities of Cu2Se-ZnSe-CNFs at a wide range of current density can be attributed to the type-I heterojunction between Cu2Se and ZnSe in composites, which can speed up electron transport. In addition, the protection from CNFs is another factor to ensure the long lifetime of Cu2Se-ZnSe-CNF anodes. The strategy of using heterojunction to promote the electrochemical properties of multi-metal sulfides may be helpful for the application of carbon composites in electrochemical catalysts and other batteries.

M. Arslan

Papers

Structural and optical properties of copper enriched ZnSe thin films prepared by closed space sublimation technique