Monocrystalline GaN(0001) thin films have been grown at 950°C on high-temperature, 100 nm thick, monocrystalline AIN(0001) buffer layers previously deposited at 1100°C on α(6H)-SiC(0001)si substrates via MOCVD in a cold-wall, vertical, pancake-style reactor. AlxGa1−xN films (0≤x≤1) were grown directly on the same SiC surface at 1100°C. Abrupt heterojunctions among the alloy composition were demonstrated. All films possessed a smooth surface morphology and were free of low-angle grain boundaries and associated oriented domain microstructures. Double-crystal x-ray rocking curve measurements for the GaN(0004) reflection for simultaneously deposited 1.4 μm films revealed FWHM values of 58 and 151 arcsec for materials grown on on-axis and off-axis material, respectively. The corresponding values for the AIN(0004) buffer layers were ≈ 200 and ≈400 arc sec, respectively. A similar relationship was found for the alloys for 0≤x≤0.2. The PL spectra of the GaN films deposited on both vicinal and on-axis substrates revealed strong bound exciton emission with a FWHM value of 4 meV. The spectra of these films on the vicinal substrates were shifted to a lower energy, indicative of films containing residual tensile stresses. A peak believed to be associated with free excitonic emission was also observed in each on-axis spectrum. Rutherford backscattering, Auger depth profiling and energy dispersive analysis were used to determine the AIN/GaN ratios in the alloys. Cathodoluminescence of solutions with x<0.5 exhibited strong near band edge emission with a FWHM as low as 31 meV. The band gaps were determined via spectral ellipsometry. Undoped GaN and A1xGa1−xN films were too resistive for accurate Hall-effect measurements. Controlled n-type Si-doping in GaN and AlxGa1−xN (for x≤0.4) was achieved for net carrier concentrations ranging from approximately 2×1017 cm−3 to 2×1019 (AlxGa1−xN) or to l × 1020 (GaN) cm−3. Mg-doped, p-type GaN was achieved with nA−nD = 3 × 1017 cm−3, p ≈ 7 Ω cm and μ ≈ 3 cm2/V·s.

High quality SrS and SrS:Ce thin films were deposited from Sr(thd)2, Ce(thd)4 and H2S via a low pressure MOCVD process. Film characteristics were found to be insensitive to the presence of the cerium dopant in the concentration range investigated. Depositions were carried out for a wide temperature range (250–550° C). Deposition rates were found to be relatively insensitive for the temperature range investigated. The films produced were found to be highly crystalline at all temperatures investigated. Deposited material showed texturing as a function of substrate material and temperature. FWHM of the <111> reflections were found to have a 2Θ values of 0.15–0.18 deg. for all temperatures. RBS and AES shows stoichiometric 1:1 SrS with less than 2% carbon and oxygen contaminates. ERD indicates the films to have 1 – 2.5% hydrogen. Films doped with 0.019 – 0.043 atom – 250 volts.

The deposition of CaS, Ga2S3, and CaGa2S4:Ce has been accomplished by MOCVD using Ca(tmhd)2, Ga(tmhd)3, and Ce(tmhd)4, with bubblers and with a liquid delivery system to control the flows. Samples were primarily characterized using x-ray fluorescence and electroluminescence measurements of the color and brightness. Deposition using the bubblers showed a definitive relationship between the Ga(tmhd)3 bubbler temperature and the Ga XRF counts. The Ca conversion shows a tenuous relationship with the Ca(tmhd)2 bubbler temperature, but the scatter of the data makes determining a correlation impractical. Use of the liquid delivery system is preferred to the bubblers because it delivered a reliable reagent flow without the same problems of degradation of the reagent over time. Analysis shows the CaS deposition is mass transport limited, while the Ga2S3 is limited by the deposition kinetics. However, application of these mechanisms to the CaGa2S4:Ce deposition system reveals that the CaGa2S4:Ce is independent of its components. Further, the deposition of CaGa2S4:Ce is found to be Ca rich under conditions which leads to low Ga/Ca ratios in the deposited film. This indicates that the conversion of Ca from Ca(tmhd)2 was catalyzed by the slight presence of Ga in the form of CaGa2S4:Ce or Ga2S3 on the surface. The Ca is thought to be deposited as CaS:Ce since there is a shift in the EL color towards green under low Ga/Ca ratios. The Ca conversion is also found to approach values predicted by the CaS deposition mechanism under conditions which lead to high Ga/Ca ratios, implying that excess Ga2S3 is needed for the deposition of CaGa2S4:Ce without any CaS:Ce inclusions.

GaInAsSb/GaSb heterostructures have been grown by metalorganic chemical vapor deposition (MOCVD). The optical properties were characterized using low temperature(71K) photoluminescence(PL) and infrared transmission spectroscopy. The FWHM of the typical PL spectrum peaked at 2.3μm is 30meV. Hall measurement results for undoped GaInAsSb layers are presented showing a p-type background and low hole concentration of 6.5 × 1015cm−3. The room temperature performances of the p-GaInAsSb/n-GaSb photodiodes are reported. Its responsivity spectrum is peaked at 2.2 5μm and cuts off at 1.7μm in the short wavelength and at 2.4μm in the long wavelength, respectively. The room temperature detectivity D* is of 1 × 109cm.Hz1/2.W−2

Quaternary GaxIn1−xAs1−ySby and ternary GaxIn1−xSb alloys have been grown by metalorganic chemical vapor deposition (MOCVD). The effects of growth parameters on the solid compositions, x, y for GaxIn1−xAs1−ySby and x for GaxIn1−x Sb alloys are described in detail. Concentrations of the reactants have major effects on the corresponding solid compositions in the two kinds of alloys. The growth temperature dependence of the solid compositions in both GaxIn1−xAs1−ySby and GaxIn1−xSb was obviously observed and the growth kinetic factor was considered to account for this dependence. It was found that III/V ratio in vapor has a great effect on x in GaxIn1−xSb alloy but little effect on x and y in GaxIn1−xAs1−ySby alloy.

Composite diamond coatings on Si3N4 substrates have been developed to minimize stresses/strains and improve wear and adhesion properties. The coatings consist of a first layer of discontinuous diamond crystallites which are anchored to the Si3N4 substrate by a second interposing layer of TiC or TiN film. A top third layer of continuous diamond film is grown epitaxially on the first layer. The diamond films and TiC or TiN films were deposited using hot filament chemical vapor deposition and laser physical vapor deposition, respectively. The TiC and TiN films were examined by X-ray diffraction. The diamond films were characterized by scanning electron microscopy and Raman spectroscopy. Adhesion of the diamond coatings was investigated using overlap polishing with diamond paste, wear against Al-12.5%Si alloy, and pull-test. The results show that after introducing an interposing layer of TiC or TiN, adhesion of diamond coatings on Si3N4 substrates is improved significantly. After polishing test against diamond paste for 4 hours, only 30% of diamond was retained with single diamond coating while 80% of diamond was found with TiN composite diamond coating. The mechanism of improvement of adhesion is discussed.

A series of amorphous hydrogenated carbon-nitrogen alloy films (a-CxNyHz) has been prepared via plasma-enhanced chemical vapor deposition from mixtures of nitrogen and acetylene. It is found that as the ratio R=N2/C2H2 is increased from zero to 100, the nitrogen incorporation into the films is increasing while the deposition rate is decreasing for 0<R<10 and is saturating at a value of about 1.0 A/sec for 10<R<100. The absorption associated with the N-H stretching mode increases while that of the C-H stretching mode decreases with increase of R. The optical constants and the energy gaps of these films have also been determined. A free energy model previously developed for the prediction of the bonding in amorphous a-CxHyalloys is extended and applied here to a-CxNyHz. Predictions are presented for the bonding of tetrahedral C(sp3), trigonal C(sp2), linear C(sp1), pyramidal N(sp 3), trigonal N(sp 2), and linear N(sp1) atoms in the alloy, and the bonding of H to these atoms.

It has been revealed that ion energy and ion flux density play an essentially critical role in SiNx deposition process of PECVD in TFT-LCD production. Ion energy and ion flux density bombarding onto substrate surface are known to be extracted from waveform of RF applied to an electrode. Using this method, authors investigated film quality of SiNx formed in the conventional parallel plate PECVD equipment. When N2+H2 or N2+Ar is employed as a carrier gas in source gas(SiH4+NH3), authors have defined normalized ion flux density as ion flux density divided by deposited SiNx molecule which must be increased to obtain high quality SiNx film while ion energy is suppressed at low level as not giving damages on the film surface. This technique has made it possible to securely form SiNx film (2500 Å) featuring dielectric breakdown field intensity of 8.5MV/cm at 250°C on a glass substrate with Cr gate interconnects of 1000 Å having vertical step structure. One of the important factors to improve film quality of SiNx deposited in PECVD is to increase ion flux density while keeping ion energy low enough to protect growing surface against any damages. Using this technique inverse-staggered TFT-array featuring field effect mobility of 0.96 •/V·s has been demonstrated which gate insulator SiNx, non-doped a-Si:H and a- Si:H(n+) were formed continuously at the same substrate temperature of 2500°C.

Low pressure metal-organic chemical vapor deposition has been used to grow dielectric thin films of the tetragonal perovskites LaSrGaO4 and PrSrGaO4 on (110) LaAlO3 using the volatile metal sources Pr(dpm) 3, La(hfa) 3•tri, Ga(dpm) 3, and Sr(hfa) 2•tet (dpm = dipivaloylmethanate, hfa = hexafluoroacetylacetonate, tet = tetraglyme, and tri = triglyme). The PrSrGaO4, a new ternary oxide, was found to have a body-centered tetragonal lattice with a = b = 3.80 and c = 12.59 Å. Epitaxial c-axis oriented growth of these materials has been revealed by both x-ray and electron diffraction, with an average surface roughness, measured by AFM, of 1.2 nm for LaSrGaO4 and 3.0 nm for PrSrGaO4. In addition to this, the ability of these materials to function as lattice-matched buffer layers for the growth of the high temperature superconductor YBa2Cu3O7−, has been explored. The superconductive properties of the YBCO layer do not indicate any degradation attributable to the buffer layers, with the onset of superconductivity displaying a sharp metal-superconductor transition at Tc = 87.3 K and 84.5 K for the LaSrGaO4 and PrSrGaO4 systems, respectively.

An essential step in the commercialisation of the MOCVD technique is the prompt availability of reliable precursors such as volatile alkoxides and diketonates for oxide deposition. Synthesis methods must be scaled by three orders of magnitude from grams to kilos to manufacture precursors for commercial devices. Impurities determine whether an identified method is viable due to the way in which they affect yield, shelf life and performance. Deleterious contaminants include free radicals, moisture damage and raw material remnants. Such considerations dominate multi-kilo synthesis but their impact may not have been perceived at an earlier stage. By particular examples we show attention to methodology can overcome these problems.

The volatility of a series of group 13–16 cubane compounds, [(R)ME]4 (M = Al, Ga; E = S, Se, Te) has been investigated by thermogravimetric analysis. The effects of the M4E4 core, the ligand (R), and molecular packing on the relative sublimation temperature and the activation energy of sublimation are discussed. For any given ligand type (e.g., [(tBu)ME] 4) volatility is dependent on the compound's molecular mass. The volatility of a homologous series (e.g., [(R)GaS] 4) is proposed to be dependent on the interlocking of the ligands in the solid state. In contrast, the energy of activation for sublimation (Ea) may be related to the molecular packing of the cubane cores in the solid state.

Volatile and thermally stable nickel complexes have been prepared by the reaction of fluorine substituted, nickel β–diketonates with neutral (poly)oxygen and (poly)nitrogen donor ligands.

These complexes, which have low melting points, have been applied as precursors in MOCVD experiments directed on nickel and nickel oxide deposition. Investigations into the deposition of NiO in porous YSZ via particle precipitation MOCVD, for the development of an anode for a planar Solid Oxide Fuel Cell, are reported.

MOCVD, one preferred technique of the present electronics industry, has not yet emerged as the thin film method of choice for group 2 element containing materials due to the demonstrable shortcomings of the available source compounds. Most specifically, the challenge presented by the group 2 element charge/ionic radius ratio must be overcome to meet the vapor pressure requirements for CVD. To date, development of group 2 precursors suitable for MOCVD has focused mainly on the use of substituted acetylacetonate (acac) complexes. Earlier, several series of somewhat volatile precursors were developed by the use of acetylacetonate complexes containing fluorinated sidegroups. These precursors, while elegantly designed for the thermal deposition of BaF2, are not ideal for the preparation of oxide thin films. This arises from their propensity to initially form MF2, which must be reacted further in situ, or in a post-deposition treatment to yield the ultimately sought metal oxide. It is of interest, therefore, to develop stable, volatile precursors lacking fluorinated ligands.

The synthesis and characterization of thermally stable, volatile, group 2 element-containing complexes is an important prerequisite for the subsequent use of these compounds in chemical vapor deposition (CVD) of superconducting metal oxides (SMO) and other electronic materials, e.g., YBa2Cu3O7-δ. and CaGa2S4:Ce. The utilization of group 2 metal ethoxide compounds {[M(OEt)2(EtOH)4]n (where M = Ca, Sr or Ba)) as precursors to additional complexes is discussed. For example, the compounds [M(tmhd)(OEt)(EtOH)]n (Htmhd = 2,2,6,6- tetramethylheptane-3,5-dione) may be obtained by reacting one equivalent of Htmhd with the metal bis(ethoxide), and these also may be reacted further with functionalized alcohols, or a second β–diketone, to form heteroleptic compounds. Additionally, the preparation and characterization of some Lewis base adducted complexes have been examined with an emphasis on the role that water plays in their isolation.

The homoleptic compound erbium{tris[bis (trimethylsilyl)]amide} displays high doping ability for incorporation of the rare earth element into epitaxially grown semiconducting host materials for fabrication of temperature-independent, monochromatic solid state optoelectronic devices. Electronic characteristics derived from erbium doped semiconducting films have been obtained. Several more volatile and lower melting representatives of this class of compounds have been synthesized, characterized by various analytical techniques and examined for their suitability to incorporate optically-active erbium centers into a semiconducting environment.

Zinc selenide doped with nitrogen deposited by organometallic vapor phase epitaxy (OMVPE) is one example which leads to a material that produces a blue emission. However, the effective incorporation of the nitrogen dopant into the zinc selenide lattice has not yet resulted in the demanded efficiency. One potential solution involves the design of a precursor introducing the nitrogen dopant bonded to zinc that survives the thermal decomposition process. Several new zinc bis(amide) compounds with the general formula Zn[N(R)(R′)]2 have been synthesized. Investigations into the thermal decomposition mechanisms of these compounds have provided insight into the potential usefulness of the designed precursor in the preparation of ZnSe:N.

Ferroelectric PbZrxTi1-x O3 (PZT) films have been deposited by chemical vapor deposition using flash vaporized metalorganic precursors. Crystalline perovskite films approximately 3000Å thick were deposited on Pt/Si substrates at 550–590°C and had dielectric coefficients in the range of 600–1900. Dielectric constant was found to increase with increasing Zr/Ti ratio, rising to the largest values near the morphotropic phase boundary. Remanent polarizations of the PZT were between 20–27 μC/cm2 and the coercive field decreased with increasing Zr/Ti ratio from 43 to 21 kV/cm. Pyroelectric coefficients were measured using the Byer-Roundy technique and ranged from 20–30 nC/cm2K. At 550°C, a direct relationship was observed between precursor composition and film composition. At 590°C, volatility of PbO became appreciable and composition of films with Zr/(Zr+Ti) = 0.3 remained near stoichiometry over a wide range of excess Pb in the precursor. However, this effect was found to diminish for higher ratios of Zr/Ti. The orientation of the PZT films deposited over a range of precursor compositions was similar with some [100] preferred orientation. In contrast, the orientation of a PbTiO3 films could be manipulated by the Pb/Ti ratio in the precursor, with [111] preferred orientations predominating at lower Pb/Ti and [ 100/001]–[111] mixed orientations at higher Pb/Ti ratios.

The possibility of growing crystallographically aligned films of good quality on polycrystalline or amorphous substrates is of great interest, both for fundamental understanding of film growth mechanisms, and for potential applications such as buffer layers for silicon-on-insulator devices and an epitaxial transition layer for cuprate superconductor thin films grown on substrates with large misfits. Deposition conditions for yttria-stabilized zirconia (YSZ) thin films were investigated and optimized, and highly (001) oriented YSZ films were reproducibly prepared on amorphous substrates by MOCVD. We believe that the formation of a highly oriented crystalline film on an amorphous substrate can be interpreted in terms of the inherent features of MOCVD process, and a working model of this process is suggested.

UV spectroscopy has been used as an in situ diagnostic to measure the gas phase concentration of 2,2,6,6-tetramethyl-3,5-heptanedionate (thd) complexes of Ba, Cu and Y in metalorganic chemical vapor deposition (MOCVD) bubbler effluent. These precursors for MOCVD synthesis of YBa2Cu37−δ (YBCO) show marked instability in gas phase concentration as a function of time during bubbler purge. The UV diagnostic technique has been applied to both a small scale test system and a commercial scale MOCVD reactor.