Organometallic Chemical Vapor Deposition Process Research Articles

Octadecyltrichlorosilane (OTS): a resist for OMCVD gold nanoparticle growth

AbstractOne application of octadecyltrichlorosilane (OTS) self‐assembled monolayers (SAMs) is its use as thin film resists. In this work, we demonstrated that OTS SAMs can be reliable resists for organo‐metallic chemical vapor deposition (OMCVD) grown gold nanoparticles (Au NPs). In optical sensing applications based on Au NPs, one candidate system consists of patterned OTS SAMs and precisely grown OMCVD Au NPs for achieving a high sensitivity. As an initial step, the OTS SAMs need to perfectly resist the OMCVD Au NP growth. Hence the optimized formation of the OTS SAMs affected by different assembly times and baking temperatures was studied by contact angle, ellipsometry, XPS, SEM, and atomic force microscopy (AFM). To demonstrate the ability of the OTS SAMs to resist OMCVD Au NP growth, the OMCVD process was carried out on two sets of samples: OTS SAMs fabricated under optimized conditions on one set and the other set without OTS SAMs. High‐resolution XPS, RBS, SEM, and ultraviolet‐visible (UV‐Vis) spectroscopy were applied to study the growth of Au NPs on the samples with and without OTS SAM resists. Copyright © 2009 John Wiley & Sons, Ltd.

A new route to high-T c superconducting Bi–Sr–Ca–Cu–O thin films: Improved deposition efficiency and film morphology using ammonia–argon mixtures as the carrier gas

Highly oriented films of the high-Tc superconductor Bi2Sr2CaCu2Ox have been prepared by a low-pressure organometallic chemical vapor deposition process using a mixture of ammonia and argon as the carrier gas together with Sr(dpm)2 (dpm-dipivaloylmethanate), Ca(dpm)2, Cu(acac)2 (acac-acetylacetonate), and triphenylbismuth as the organometallic precursors. By introducing ammonia into the carrier gas, a significant improvement in the volatility and thermal stability of both Sr(dpm)2 and Ca(dpm)2 is observed. Typical required source temperatures for Sr(dpm)2 and Ca(dpm)2 with the introduction of ammonia are about 40–50 °C lower than the source temperatures of the precursors without the introduction of ammonia. Enhancement of source volatility for Cu(acac)2 is also observed. After annealing at 865 °C in flowing oxygen, the films consist predominantly of the Bi2Sr2CaCu2Ox phase and exhibit high preferential orientation of the crystallite c axes perpendicular to the substrate surface. Four-probe resistivity measurements indicate the onset of film superconductivity at ∼110 K and zero resistivity achieved at 74 K.

Spectroscopic study of plasma-enhanced organometallic chemical vapor deposition for superconducting thin film formation

Plasma-enhanced organometallic chemical vapor deposition process has been developed to prepare high Tc superconducting films. The volatile organic precursors of Y(fod)3, Ba(hfa)2, and Cu(hfa)2 were decomposed with a microwave discharge plasma. Optical emission spectroscopy was used to determine the identity of the species produced during the vaporization and decomposition process. In this process, Y, Y+, Ba, Ba+, Cu, and Cu+ species were detected. After annealing in air, the films deposited on the (100) SrTiO3 substrate had preferential orientation of the crystalline c-axis perpendicular to the substrate surface. The characterization of this process is discussed comparing a hollow cathode YBaCuO plasma with the laser ablation experiments published.

Deposition of high-T c superconducting Y-Ba-Cu-O thin films at low temperatures using a plasma-enhanced organometallic chemical vapor deposition approach

A plasma-enhanced organometallic chemical vapor deposition process is reported for the preparation of YBa 2Cu 3O 7-x thin films using two differing rf plasma coupling configurations. For films grown under a direct plasma glow, the YBa 2Cu 3O 7-x phase is not produced in the asdeposited state. However, when plasma-activated nitrous oxide is used as the reactant gas in a downstream reactor configuration, superconducting YBa 2Cu 3O 7-x films are formed in situ at a substrate temperature of 610°C. Such films have a low carbon content and a mirror-like surface which is free of voids. These preliminary results indicate that the low temperature fabrication of high-T c superconducting oxide films by plasma-enhanced organometallic chemical vapor deposition is feasible.

Low Temperature Preparation of Y‐Ba‐Cu‐0 High Tc Superconducting Thin Films by Plasma‐Enhanced Organometallic Chemical Vapor Deposition

AbstractWe report here a plasma‐enhanced organometallic chemical vapor deposition process for the preparation of YBa2Cu3O7‐x thin films using two rf plasma coupling configurations. For the films grown under a direct plasma glow, the YBa2Cu3O7‐x phase is not found in the as‐deposited state. However, by employing plasma‐activated nitrous oxide as the reactant gas, superconducting YBa2Cu3O7‐x films having a low carbon content and a mirror‐like surface have been prepared in‐situ at a substrate temperature of 610°C using an organometallic chemical vapor deposition process.

GaAs crystal growth from coordination compounds using the organometallic chemical vapor deposition process for solar cells

GaAs thin layers have been obtained from coordination compounds (adducts) using the organometallic chemical vapor deposition process (O.M.C.V.D.). That is the first step of a study going on to realize GaAlAs/GaAs solar cells. The preparation of the compounds has shown that the bond strength energy between the Ga and As atoms in the molecule is very important for use in a chemical vapor deposition process. The layers were p type and the use of As Et 3 occurs in the chemical equilibrium of the vapour phase to obtain n type material. The crystallographic orientation of the substrates can influence the growth mechanisms of the layers.

Interface properties of n-ZnSe–p-Ge heterojunctions grown by organometallic chemical vapor deposition

Aluminum-doped, n-type ZnSe layers ranging in thickness from several thousand Ångstroms to several microns were grown epitaxially on differently oriented p-type Ge substrates by a low temperature, low pressure organometallic chemical vapor deposition process. The surface morphology and photoluminescence spectra reveal differences between the ZnSe films grown on (100)Ge substrates and those grown on (111)Ge substrates. Photoluminescence spectra of the former films show strong band gap luminescence, whereas the latter films are characterized by a reduced band gap luminescence intensity and an enhanced intensity in the self-activated region. The lattice structure of the ZnSe–Ge interface has been studied by high resolution transmission electron microscopy, and the electrical characteristics of the corresponding n-ZnSe–p-Ge heterojunctions have been measured. Heterojunctions formed on (100) oriented substrates show good diode behavior with dark saturation currents of 1×10−11 A/cm2. Heterojunctions formed on (111) substrates are characterized by poor diode behavior with dark saturation currents of the order of 4×10−8 A/cm2. The difference in the electrical transport properties is attributed to the distinctly different defect structure at the ZnSe–Ge heterojunction interface.

Growth and doping of ZnSe and ZnS xSe 1- x by organometallic chemical vapor deposition

Nominally undoped ZnSe and ZnS x Se 1- x and low-resistivity n-type ZnSe doped with aluminum has been grown epitaxially on GaAs substrates by a low temperature, low-pressure organometallic chemical vapor deposition (OM-CVD) process. The layers are typically ⩽5 μm thick and exhibit a strong bandedge photoluminescence peak dominated by the I 2 bound exciton line. This result indicates that ZnSe prepared by OM-CVD has a better quality than ZnSe prepared by most other methods where donor-acceptor pair bands and the self-activated (SA) PL dominate the PL spectrum. Recent results on p-type doping experiments suggest that nitrogen is a substitutional shallow acceptor with an activation energy of ∽110 meV. This paper discusses the merits of the OM-CVD process and compares the results obtained so far with those on ZnSe crystals or epitaxial layers prepared by other methods.

Preparation of low-resistivity n-type ZnSe by organometallic chemical vapor deposition

Low-resistivity n-type ZnSe with p<0.05 W cm and n≳1017 cm−3 has been grown epitaxially on (100) GaAs substrates by a low-pressure low-temperature organometallic chemical vapor deposition process. Triethylaluminum is used as a dopant. The as-grown layers show a strong near-band-gap photoluminescence peak. The much weaker photoluminescence intensity at longer wavelength indicates that the concentration of deep centers is lower than in doped ZnSe prepared by other methods.

Organometallic vapor deposition of epitaxial ZnSe films on GaAs substrates

Smooth epitaxial single-crystalline layers of (100) ZnSe on (100) GaAs substrates are grown by a new low-pressure low-temperature organometallic chemical vapor deposition process. The strong band-edge photoluminescence peak and the absence of any substantial luminescence intensity at longer wavelengths indicate an absence of deep trapping centers which is typically not observed in other CVD growth.