Deposition Of Uniform Thin Films Research Articles

Slot-die coated scalable hole transporting layers for efficient perovskite solar modules

We demonstrate herein the fabrication of large-area (up to 30 cm2) organic-semiconductor-based films using slot-die coating – an established and highly scalable printing technology that enables deposition of uniform thin films on various substrates.

Design and Construction of Home-Made Spin Coater for OLED Production

This study devotes to the design and fabrication of a spin coating equipment using locally available materials for the deposition of uniform thin films on several substrates and also the production of organic light emitting diodes (OLEDs) using this home-made device. The equipment consists of a brushed direct current (BDC) motor with high speed, chuck (substrate

Modeling and the main stages of spin coating process: A review

Spin coating is a technique employed for the deposition of uniform thin films of organic materials in the range of micrometer to nanometer on flat substrates. Typically, a small amount of coating material generally as a liquid is dropped over the substrate center, which is either static or spinning at low speed. The substrate is then rotated at the desired speed and the coating material has been spread by centrifugal force. A device that is used for spin coating is termed a spin coater or just a spinner. The substrate continued to spin and the fluid spins off the boundaries of the substrate until the film is reached the required thickness. The thickness and the characteristics of coated layer (film) are depending on the number of rotations per minute (rpm) and the time of rotation. Therefore, a mathematical model is obtained to clarify the prevalent method controlling thin film fabrication. Viscosity and the concentration of (solution) spin coating material are also affecting the thickness of the substrate. This article reviews spin coating techniques including stages in the coating process such as deposition, spin-up, stable fluid outflow (spin-off), and evaporation. Additionally, the main affecting factors on the film thickness in the coating process are reviewed.

Numerical analysis for optimization of the sidewall conditions in a capacitively coupled plasma deposition reactor

Capacitively coupled plasma (CCP) is mainly being used in the semiconductor industry for plasma-enhanced chemical vapor deposition of uniform thin films. Because a discharge volume in the standard configuration of a CCP reactor is surrounded not only with electrode surfaces but also with a sidewall, the sidewall conditions affect the deposition rate profiles noticeably. By toggling the boundary condition from a grounded conductor to dielectrics with the variations of the relative permittivity and the thickness, we compare the spatial profiles for the species densities, ionization rate, power absorption, and particle fluxes in a SiH4/He CCP. Through the SiH4/He CCP fluid model, it is found that a thick and low-permittivity insulator achieves the most uniform plasma density distribution in the interelectrode region and, consequently, the best uniformity in the deposition rate profile of an a-Si:H film. As a validation, experimental results are compared with fluid modeling results, and they match well. For additional validation, a particle-in-cell simulation of pure Ar discharge is also performed. Although simulation conditions are totally different from those of the SiH4/He fluid model, it consistently demonstrates that the dielectric sidewall brings about more uniform distributions of the plasma parameters than the grounded sidewall.

Flexible thin film solar cells on cellulose substrates with improved light management

Cellulose substrates for PV applications present a fibrous surface texture that is not suitable for the uniform deposition of thin-film solar cells causing poor device performance. However, uniform thin-film deposition and efficient light management for solar cells can be achieved on cellulose substrates by transferring well-known surface textures that provide an adequate surface for thin film solar cell deposition and also, provide light scattering properties into the cellulose surface. In this work, we study the properties of crater-like textures transferred onto cellulose substrates by nanoimprint lithography and the corresponding effect on the J–V and EQE characteristics of amorphous silicon thin-film solar cells. The prototype solar cells are deposited on cellulose substrates and the results are compared with the results of such solar cells deposited on flat glass substrates. The results show that the J–V characteristics of solar cells deposited on planar as well as textured glass substrates are well reproduced. Due to the process routine, the solar cells on the cellulose substrate with nanoimprinted textures show an increase in the short circuit current density and power conversion efficiency over previous results in our laboratory.

Low pressure chemical vapor deposition of silicon carbide thin films from hexamethyldisilane

Silicon carbide thin films were grown by low pressure chemical vapor deposition using hexamethyldisilane Me 3SiSiMe 3 as the single-source precursor. Deposition of uniform thin films on Si(1 1 1) substrates was carried out at temperatures 1123–1323 K in a hot-wall reactor. The growth rates were 0.9–55 nm min −1 depending on the conditions employed. Estimated energy of activations is 110 kJ mol −1. Bulk elemental composition of the thin films, studied by an electron probe X-ray microanalyzer, is best described as SiC x ( x=0.8−2.3). The Si/C ratio increased with increasing temperature of deposition. The films were cubic polycrystals, a=0.435−0.438 nm, as indicated by scanning transmission electron microscopy, electron diffraction and X-ray diffraction. The lattice parameter decreased with increasing temperature of deposition. Elemental distribution within the films, studied by Auger depth profiling and X-ray photoelectron spectroscopy, was uniform. Gas phase products H 2, CH 4, C 2H 4, Me 3SiH and Me 4Si were identified and possible reaction pathways were proposed.

Tungsten nitride thin films prepared by MOCVD

Polycrystalline tungsten nitride thin films were grown by low pressure metallo-organic chemical vapor deposition (MOCVD) using (tBuN)2W(NHtBu)2 as the single-source precursor. Deposition of uniform thin films on glass and silicon substrates was carried out at temperatures 723–923 K in a cold-wall reactor, while the precursor was vaporized at 333–363 K. The growth rates were 2–10 nm/min depending on the condition employed. Bulk elemental composition of the thin films, studied by wavelength dispersive spectroscopy (WDS), is best described as WNx (x = 0.7–1.8). The N/W ratio decreased with increasing temperature of deposition. X-ray diffraction (XRD) studies showed that the films have cubic structures with the lattice parameter a = 0.414–0.418 nm. The lattice parameter decreased with decreasing N/W ratio. Stoichiometric WN thin films showed an average lattice parameter a of 0.4154 nm. X-ray photoelectron spectroscopy (XPS) showed that binding energies of the W4f7/2, W4f5/2, and N1s electrons were 33.0, 35.0, and 397.3 eV, respectively. Elemental distribution within the films, studied by secondary ion mass spectroscopy (SIMS) and Auger spectroscopy depth profilings, was uniform. The SIMS depth profiling also indicated that C and O concentrations were low in the film. Volatile products trapped at 77 K were analyzed by gas chromatography–mass spectroscopy (GC–MS) and nuclear magnetic resonance (NMR). Isobutylene, acetonitrile, hydrogen cyanide, and ammonia were detected in the condensable mixtures. Possible reaction pathways were proposed to speculate the origin of these molecules.

Laser-ablation deposition of uniform thin films of Bi 2Sr 2CaCu 2O x

This paper reports detailed modelling and supporting experimental results of a novel rotational technique used to prepare uniform thin film superconductors by laser ablation. The method produces homogeneous films over an area of several square centimeters. We have applied the technique to the preparation of (2212) BiSrCaCuO thin films. We show that layers deposited in 10 min and annealed for 20 min at a temperature of 850°C, produced films with superior properties to those films processed at temperatures only varying slightly from this value.

Laser-monitored deposition of Parylene thin films

A method has been developed for the deposition of uniform thin films of Parylene C by the use of laser monitoring. By monitoring the reflectivity of metal-coated substrates during growth of the polymer films, effective anti-reflecting coatings have been deposited which have appreciably improved some properties of chalcogenide and Gd-Co alloy films. The optimum conditions for Parylene C film deposition were found by studying the effect of dimer source temperature and system pressure on the deposition rate and film quality and uniformity. These results are reported and the apparatus is described.

Large Area Thin Films of Highly Uniform Thickness Vacuum Deposited in a Stationary System

A vacuum system for the deposition of uniform thin films from a single, small area source without moving parts has been developed. By interposing a stationary tube and baffle of appro-priate dimensions and temperature between the source and substrate, it is possible to deposit films that have thickness uniformities over large substrate areas which heretofore have only been achieved through use of multiple sources and/or moving parts. Thin films of aluminum, copper and gold have been deposited with this system and thickness uniformities of better than ±2% over 14 cm at a source to substrate distance of 25 cm have been observed to date. There are indications that further improvements are possible through optimizations of tube parameters.