Search results for "thin film"

Disclosing of optical properties of metal/dielectric heterostructures by Spectroscopic Ellipsometry enhanced by Surface Plasmon Resonance

2013

3D photonic crystal intermediate reflector for micromorph thin-film tandem solar cell

2008

The concept of 3D photonic intermediate reflectors for micromorph silicon tandem solar cells has been investigated. In thin-film silicon tandem solar cells consisting of amorphous and microcrystalline silicon with two junctions of a-Si/μc-Si, efficiency enhancements can be achieved by increasing the current density in the a-Si top cell. It is one goal to provide an optimized current matching at high current densities. For an ideal photon-management between top and bottom cell, a spectrally selective intermediate reflective layer (IRL) is necessary, which is less dependent of the angle of incidence than state-of-the-art thickness dependent massive interlayers. The design, preparation and cha…

Fabrication of CZTSe/CIGS Nanowire Arrays by One-Step Electrodeposition for Solar-Cell Application

2021

The paper reports some preliminary results concerning the manufacturing process of CuZnSnSe (CZTSe) and CuInGaSe (CIGS) nanowire arrays obtained by one-step electrodeposition for p-n junction fabrication. CZTSe nanowires were obtained through electrodeposition in a polycarbonate membrane by applying a rectangular pulsed current, while their morphology was optimized by appropriately setting the potential and the electrolyte composition. The electrochemical parameters, including pH and composition of the solution, were optimized to obtain a mechanically stable array of nanowires. The samples were characterized by scanning electron microscopy, Raman spectroscopy, and energy-dispersion spectros…

Phase separation in thin films: Effect of temperature gradients

2013

We study the phase-separation kinetics of a binary (AB) mixture confined in a thin film of thickness D with a temperature gradient. Starting from a Kawasaki-exchange kinetic Ising model, we use a master-equation approach to systematically derive an extension of the Cahn-Hilliard model for this system. We study the effect of temperature gradients perpendicular to the film with "neutral" (no preference for either A or B) surfaces. We highlight the rich phenomenology and pattern dynamics which arises from the interplay of phase separation and the temperature gradient.

Magnetoresistivity and crystal structure of epitaxial La0.67Ca0.33MnO3 films

1998

Abstract We investigated thin-film growth of doped manganites by sputter deposition on SrTiO 3 (1 0 0), MgO (1 0 0) and r -plane Al 2 O 3 (1 0 1¯2) substrates and found an in-plane-oriented growth. The unit cell of the films showed distortions from the simple cubic perovskite structure, represented by a tetragonal unit cell with a′ = b′ = √2 a ; c′ = 2 a . By scanning electron microscopy we investigated the growth morphology of the films. We determined the magnetotransport properties above and below room temperature. Transport at high temperatures is best described by polaron hopping.

Preparation of thin films of the ternary heavy fermion system CeNi 2 Ge 2

1998

Ge2 layers on W(110). In order to produce well-ordered and atomically clean surfaces of the Ce-based intermetallic system the growth was performed under UHV conditions (p<2×10-11 mbar). Both the polycrystalline CeNi2Ge2 compound and the individual elements Ce, Ni, and Ge were used as evaporants. The characterisation of the layers was made with LEED, SEM, and XPS. We find a significant influence of the substrate temperature and the evaporation power on the growth characteristics. The compound material CeNi2Ge2 exhibits complicated behaviour when evaporated. Under carefully selected growth conditions we obtain well-ordered films with a stoichiometry of Ce:Ni:Ge=1:2:2 and a (001) oriented surf…

Growth of thin films of single-chain magnets on functionalized silicon surfaces

2018

A one-pot strategy for the direct growth of continuous and regular thin films of a neutral oxamato-bridged heterobimetallic chain, synthesized from Co2+ nitrate and the tetramethylammonium salt of the anionic copper(II) complex (Me4N)2[Cu(2,6-Et2pa)2]·6H2O (1) (2,6-Etpa = N-2,6-diethylphenyloxamate) over Si(111) surfaces functionalized with carboxylic acid terminating groups has been developed. Variation of the growth conditions can provide important differences in the morphology of the obtained films when working in H2O at 20 °C. An anisotropic growth of 1-D fibers is observed under stoichiometric conditions (Co2+/1 = 1:1), while an isotropic growth of 3-D particles occurs for an excess of…

Impact of transparent conductive oxide on the admittance of thin film solar cells

2010

Abstract The impact of transparent electrically conducting oxide (TCO) on the admittance measurements of thin film p–i–n a-Si:H solar cells was investigated. Admittance measurements on solar cell devices, with different area and geometry, in a wide range of frequencies and biases were performed. The admittance measurements of the investigated solar cells, which use the TCO as an electrical contact, showed that the high frequency admittance per area unit depends on the area. This effect increases both with the probe frequency and the size of the solar cells. Transmission line model valid for strip geometry which explains how the resistivity of the TCO layer impacts the measured admittance of…

Multiple Crack Localization and Debonding Mechanisms for Thin Thermal Coating Films

2020

Experimental tests, carried out on small scale alloy specimens covered on one side with a thin thermal coating, have shown complex failure mechanisms. The failure mechanisms observed are due to the competition between two fracture mechanisms. The two mechanisms are: (i) Vertical tensile coating surface cracks and (ii) debonding shear decohesion mechanisms along the interface between the coating and the substrate. The present paper analyzes the mechanical problem of the nonlinear behavior thin film on a stiff substrate adopting a computational approach. Namely, incremental 2D nonlinear finite element simulations. The stiff superalloy substrate is modeled as a thermo-elastic material. The coa…

Formation of metastable structures by phase separation triggered by initial composition gradients in thin films.

2012

Phase separation kinetics of a binary (A,B) mixture contained in a thin film of thickness D induced by a quench from the one-phase region into the miscibility gap is studied by simulations using a Cahn-Hilliard-Cook model. The initial randomly mixed state (50% A, 50% B) contains a concentration gradient perpendicular to the film, while the surfaces of the film are "neutral" (no preference for either A or B). In thermal equilibrium, a pattern of large A-rich and B-rich domains must result, separated by domain walls oriented perpendicularly to the external surfaces of the thin film. However, it is shown that for many choices of D and the strength of the initial gradient Ψ(g), instead a very l…