Deposition of Thin Films Materials used in Modern Photovoltaic Cells

The energy and the angular distribution of atoms are considered two parameters most influential in optimizing the sputtering and subsequently on the deposit, resulting in films having the desired properties (homogeneity in thickness, composition identical to that of the evaporated material). Moreover, a great influence on the shape and quality of thin films is obtained. In this work, a simulation with the Monte Carlo (MC) software SRIM (Stopping and Range of Ions in Matter) is used to calculate the sputtering yield for different energies, and angular distributions of atoms of photovoltaic devices materials (CdS and CIGS) bombarded by different gas particles (Ar, Xe, and Ne). Our results showed that when arriving at a certain energy value Emax, the sputtering yield will be in maximum Y1max. Applying this Emax and variation in the angular distribution, we will obtain θmax corresponding to the maximum sputtering yield Y2max. These two values (Emax, θmax) give the maximum of atoms sputtered, and as a result, the films will be uniform. The obtained results are in very high agreement with other works, which validates our calculations

Sputtering of semiconductors, conductors, and dielectrics for the realization of electronics components thin-films

With the application of Monte Carlo simulation codes represented by SRIM (Stopping and Range of Ion in Matter) and SIMTRA (Simulation of the Metal Transport) software, the effect of diver’s parameters on the surface structure of thin films are studied in 3D form with the magnetron sputtering process. Inside a vacuum chamber, 105 particles of various gas which are Argon (Ar), Xenon (Xe), and Neon (Ne) are injected, the target contained materials used for the manufacturing of electronic components like semiconductors: Silicon (Si) and Germanium (Ge), conductors: Copper (Cu) and dielectric: silicon dioxide (SiO2) materials respectively. The results obtained in this work show that the energies of the particles, the incidence angles, and the gas nature are some of the principles and important parameters which affect the sputtering yield and hence the number of ejected atoms from the target, increasing the energy or incidence angles will increase the total number of ejected atoms, using Xenon gas gives best results comparing to Argon and Neon and also the sputtering yield of the copper conductor is superior to semiconductors and dielectric materials each to each

He Scattering from Random Adsorbates, Disordered Compact Islands and Fractal Submonolayers: Intensity Manifestations of Surface Disorder

A theoretical study is made on He scattering from three fundamental classes of disordered ad-layers: (a) Translationally random adsorbates, (b) disordered compact islands and (c) fractal submonolayers. The implications of the results to experimental studies of He scattering from disordered surfaces are discussed, and a combined experimental-theoretical study is made for Ag submonolayers on Pt(111). Some of the main theoretical findings are: (1) Structural aspects of the calculated intensities from translationally random clusters were found to be strongly correlated with those of individual clusters. (2) Low intensity Bragg interference peaks appear even for scattering from very small ad-islands, and contain information on the ad-island local electron structure. (3) For fractal islands, just as for islands with a different structure, the off-specular intensity depends on the parameters of the He/Ag interaction, and does not follow a universal power law as previously proposed in the literature. In the experimental-theoretical study of Ag on Pt(111), we use first experimental He scattering data from low-coverage (single adsorbate) systems to determine an empirical He/Ag-Pt potential of good quality. Then, we carry out He scattering calculations for high coverage and compare with experiments. The conclusions are that the actual experimental phase corresponds to small compact Ag clusters of narrow size distribution, translationally disordered on the surface.Comment: 36 double-spaced pages, 10 figures; accepted by J. Chem. Phys., scheduled to appear March 8. More info available at http://www.fh.huji.ac.il/~dani

Simulation of reconstructions of the polar ZnO (0001) surfaces

Surface reconstructions on the polar ZnO(0001) surface are investigated using empirical potential models. Several possible reconstructions based around triangular motifs are investigated. The quenching of the dipole moment in the material dominates the energetics of the surface patterns so that no one particular size of surface triangular island or pit is strongly favoured. We employ Monte Carlo simulations to explore which patterns emerge from a high temperature quench and during deposition of additional ZnO monolayers. The simulations show that a range of triangular islands and pits evolve in competition with one another. The surface patterns we discover are qualitatively similar to those observed experimentally

Bioinspired scattering materials: light transport in anisotropic, disordered systems

The study of light propagation in disordered media has attracted the interest of many researchers for its relevance to fundamental and applied problems, ranging from imaging through turbid media to the fabrication of white paint. Scattering in a disordered system is determined by the spatial distribution and the scattering properties of its building blocks. To date, most efforts on scattering optimisation have focused on isotropic, high refractive index systems. This thesis investigates the importance of anisotropy in increasing the scattering efficiency of a system, with a particular focus on low refractive index media and their use as sustainable, white materials. Nature provides a striking example of how to exploit anisotropy to achieve scattering optimisation: with the intra-scale chitin network of the beetle genus Cyphochilus. In this thesis, after showing that this network exhibits the highest scattering efficiency found in nature thus far, a systematic numerical investigation was performed to understand the importance of both single-particle and structural anisotropy in scattering optimisation. In particular, this numerical analysis unveiled that ensembles of anisotropic particles show higher reflectance compared to their isotropic counterpart, whilst using less material. Based on these findings, the optical properties of bioinspired, scattering systems — obtained both via polymer phase separation and a combination of sequential vacuum filtration and freeze-drying — were investigated. Notably, the reported materials achieve scattering properties comparable to those found in nature, showcasing the potential of using biopolymers to produce sustainable, biocompatible white materials. In addition, the presented bioinspired systems are an interesting platform for fundamental studies, allowing to investigate light transport in anisotropic media.European Research Council grant awarded to Dr Silvia Vignolin