Amorphous germanium nitride thin films are prepared by plasma enhanced chemical vapor deposition from tetrakis(dimethylamido)germanium, Ge(NMe2)4, and an ammonia plasma at substrate temperatures as low as 190°C with growth rates >250 Å/min. N/Ge ratios in the films are 1.3 and the hydrogen contents are 13 atom %. The hydrogen is present primarily as N-H. The refractive indexes are close to the bulk value of 2.1, and the band gap, estimated from transmission spectra, is 4.8 eV.

Use of metal-organic precursor materials has permitted thermal CVD of many metal nitrides at remarkably low temperatures and without corrosive by-products. Metallic TiN, VN, Nb3N4 and Mo2N3; semiconducting GaN and Sn3N4; and insulating AIN, Zr3N4, Hf3N4 and Ta3N5 can be deposited at temperatures typically in the range 100 to 400 C. Deposits free of carbon are obtained by transamination reactions of metal dialkylamido precursors with a sufficiently large excess of ammonia. The resulting TiN films are good diffusion barriers, and provide low contact resistance between metals and silicon.

Transparent semiconducting oxide films, such as SnO2, ZnO and TiO2, are often made by MOCVD for use in solar cells, energy-efficient window coatings and electro-optical displays. These wide band-gap semiconductors can be doped to n-type conductivity by a variety of dopant elements. Fluorine is the dopant which produces materials with the highest electron mobility, conductivity and transparency, by substituting for oxygen. Certain organic fluorine compounds have been found to be very effective fluorine dopants for these CVD reactions, yielding films with very shallow donors having nearly 100 % electrical activity.

Precursors for the CVD of alkaline earth metal oxides, particularly barium, lack the volatility and stability needed for reproducible deposition of superconducting, ferroelectric or magnetic oxides. Use of ammonia or volatile amines as carrier gases greatly enhances the volatility and stability of betadiketonates of barium, strontium and calcium, providing high and stable transport rates for source temperatures below 100 C, even for non-fluorinated ligands.

Low-pressure chemical vapor deposition (LPCVD) of InN and laser-assisted LPCVD on GaAs(110) and Si(100) using HN3 and trimethyl indium (TMIn) has been studied with XPS, UPS and SEM. Without 308-nm excimer laser irradiation, InN film was built on the GaAs but not on Si surface under the present low-pressure conditions. When the photon beam was introduced, InN films with In:N atomic ratio of 1.0±0.1 and a thickness of more than 20 Å (the limit of the electron escaping depth for the In3d X-ray photoelectrons) were formed on Si(100) surface. In both cases, the formation of surface nitrides at the initial film growth processes was clearly indicated in the XPS spectra. The He(II) UP spectra taken from InN films on GaAs and Si are nearly identical and agree well with the result of a pseudo-potential calculation for the InN valence band. The corresponding SEM pictures showed smooth InN films on GaAs(110), while grains with diameter of ∼100 nm were observed for InN on Si(100).

Plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD) has been successfully employed for the deposition of (100) oriented barium strontium titanate (BST) thin films on a variety of substrate and electrode materials. The incorporation of O2 plasma, which was used as oxidation reactant, has helped to reduce the required temperature for deposition of high-quality STO and BST thin films. This low temperature processing may make it possible to integrate BST on Si and GaAs. BST films with low leakage current densities of about 10−7 A/cm2 at 2-volt (about 105 V/cm) operation were obtained from PE-MOCVD processing. Moreover, the BST results of capacitance-temperature (C-T) measurements show that most of the PE-MOCVD BST films have Curie temperatures of about 30–35°C and a peak dielectric constant of 600–800 at zero bias voltage, The sharp transition in the C-T data indicates that the BST films may have a high induced pyroelectric coefficient at room temperature, which is highly desirable for uncooled IR imaging arrays. The x-ray diffraction and Rutherford backscattering spectrometry results show that the BST film composition reproducibility was well controlled at around Ba0.75Sr0.25TiO3 with a 4% variation. Device quality BST thin films with the thickness of 1000–2000 Å were produced. These results indicate that PE-MOCVD has high potential to be further developed and promoted as a production deposition technique providing high permittivity dielectric thin films for microelectronics and IR sensor industries.

Highly oriented PbTiO3 (PT) thin films have been successfully grown on Si(100) using MOCVD technique at as low as 450°C. Titanium isopropoxide, Ti(C3H7O)4, tetraethyl lead, Pb(C2H5 )4, and pure oxygen were chosen as precursor materials in this work. The resulting film chemistry and texture were found to be strongly dependent on Pb/Ti source flow ratio and growth temperature.

Ba1−xSrxTiO3 thin films were deposited over the entire solid solution range by low pressure metal-organic chemical vapor deposition. The metal-organic precursors employed were titanium tetraisopropoxide and barium and strontium(hexafl uoroacetylacetonate)2·tetraglyme. The substrates used were LaAlO3 and (100) p-type Si. Ba1−xSrxTiO3 films deposited on LaAlO3 were epitaxial, while the films deposited on Si showed no texture. Auger spectroscopy indicated that single phase Ba1−xSrxTiO3 films did not contain detectable levels of fluorine contamination. The dielectric constant was found to depend upon the solid solution composition x, and values as large as 220 measured at a frequency of 1 MHz were obtained. The resistivities of the as-deposited films ranged from 103 to 108 Ω-cm. Temperature dependent resistivity measurements indicated the films were slightly oxygen deficient.

Polycrystalline thin films of BaTiO3 were deposited on fused quartz substrates at 600°C by metalorganic chemical vapor deposition (MOCVD). The films were characterized by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), secondary ion mass spectroscopy (SIMS) and Raman spectroscopy. Films prepared in the early stages of this study that had appeared to contain only crystalline BaTiO3 by XRD were found to have nonuniform composition and microstructure through the film thickness by SIMS and TEM. The MOCVD system was then modified by installing a process gas bypass apparatus and an elevated pressure bubbler for the titanium isopropoxide precursor. A 1.2 μm thick BaTiO3 film prepared in the modified system demonstrated much improved compositional and microstructural uniformity through the thickness of the film. This film had a columnar microstructure with grain widths of 0.1–0.2 μm and exhibited tetragonality as detected by Raman spectroscopy.

Properties of undoped– and doped–ferroelectric PbZr1−xTixO3. films, with both Pt or RuO2 electrodes, were compared, with a view to understand the reasons for degradation of ferroelectric films. Donor–doped (e.g., Nb5+ at Ti4+ site) PbZr1−xTixO3 films, for which the PbO loss has been compensated, showed higher resistance to fatigue and low leakage currents compared to those of undoped films. The fatigue of ferroelectric films, a decrease in switchable polarization with increasing number of polarization reversals, has been attributed to the migration of oxygen vacancies and their entrapment at various interfaces (e.g., electrode/ferroelectric interface) that are present in the film.

By the solid source MOCVD technique, we have deposited 2000 – 3000 Å thick single phase SrxBa1−xNb2O6 (SBN) films on (100) MgO substrates using tetramethylheptanedionate (thd) sources. X-ray diffraction (XRD) 2θ scans indicated that these films were completely (001) oriented. XRD Φ scans, however, showed the films contained four in-plane grain orientations whose volume fractions could be controlled by altering the Sr/(Sr+Ba) and Nb/(Sr+Ba) ratios in the source powders. The in-plane volume fractions did not change with the deposition rate or the cooling rate. Films with composition Sr0 58Ba0.42Nb1.94O6 had mainly two in-plane orientations. Optical waveguiding behavior was demonstrated in these films. Refractive indices were found to be no= 2.20 and ne = 2.13, as compared to no = 2.31 and ne = 2.27 for bulk SBN60.

Stoichiometric vapor deposition of LiTaO3 is demonstrated by thermal evaporation of volatile LiTa(OButn)6, controlled vapor phase partial-hydrolysis, and subsequent polycondensation reactions on a heated substrate surface. Fully dense, amorphous LiTaO3 film of up to 34 μm thick can be obtained at high deposition rate of 23 μm per hour. Single phase LiTaO3 films are obtained by annealing as deposited films. The vapor phase species responsible for the stoichiometric vapor deposition appeared to be Li2Ta2(OButn)12 from variable temperature mass spectrometry results.

Lead titanate (PbTiO3) has been grown on a variety of substrates by using the metalorganic chemical vapor deposition (MOCVD) technique. The substrates employed included Si, GaAs, MgO, fused-quartz, sapphire, and KTaO3. Raman spectra from these heterostructures are presented. All of the films exhibited the strong, narrow spectral features characteristic of PbTiO3 perovskite-oxide crystals and indicative of high crystalline quality. Temperature behaviors of the Raman modes, including the socalled “soft-mode”, were studied. A “difference-Raman” technique was used to distinguish the contributions of the PbTiO3 film and the KTaO3 single-crystal substrate.

Results of ongoing investigations of a new method for processing molecular solids to form refractory thin films are presented. We have extended past work on boron nitride and alumina growth from molecular solids induced by synchrotron radiation (SR), to silica growth from tetramethylsilane and water at 80 K. Also reported are experiments where alumina is formed using 4.64 eV laser irradiation. The majority of the results suggest that with SR, the film growth is induced by secondary electrons from the substrate, whereas laser light excites the film growth by direct photolysis. Implications of this will be discussed.

Ferroelectric Barium titanate (BaTiO3) thin films have potential applications in optical devices such as frequency doublers. Second harmonic generation (SHG) in MOCVD grown epitaxial thin films of BaTiO3 on MgO substrates is reported at an incident wavelength of 1.064 microns. A number of as-grown films show substantial second harmonic signal. Angular dependence of second harmonic intensity from as-grown films reveals that the orientation of the c-axis in these films are dependent on the growth conditions. We have examined the effect of heating and corona poling on the second harmonic generated by the samples. A higher level of SHG was observed during application of the electric field. On the removal of the poling field the second harmonic signal relaxes back. This behavior may indicate substrate-induced strain stabilization of domains.

Transparent and highly specular PbTiO3 thin films were deposited on sapphire, platinum and ruthenium oxide-coated silicon wafers by hot-wall metallorganic chemical vapor deposition (MOCVD). Lead bis-tetramethylheptadionate and titanium ethoxide were used as chemical precursors. Films were deposited over a range of experimental conditions. X-ray diffraction (XRD) was used to determine the phases present in the films; Scanning Electron Microscopy (SEM) was used to examine the surface morphology and Energy Dispersive Spectroscopy (EDS) was used to determine the composition. Optical spectra were obtained to confirm the highly dense and transparent nature of the films. The chemical stability of the ruthenium oxide substrates in the MOCVD environment as well as the existence of a high-temperature deposition regime for composition control are also discussed.

Aluminum nitride films were deposited on Si (100) and sapphire (1102) substrates by low pressure chemical vapor deposition using the metalorganic precursor trisdimethylaluminum amide, [(CH3)2AlNH2]3. Depositions were carried out in a cold wall reactor with substrate temperatures between 500 and 700 °C and precursor temperatures between 50 and 80 °C. The films were analyzed by X-ray photoelectron spectroscopy, X-ray diffraction, optical microscopy and scanning electron microscopy. The films were generally smooth and adherent with colors ranging from transparent to opaque grey. Cracking and spallation were seen to occur at high film thickness. Deposition rates ranged from 20 to 300 Å/min and increased with both precursor and substrate temperature. Carbon concentrations were small, < 5 at. %, while oxygen concentrations were higher and showed a characteristic profile versus depth in the film. High temperature compatibility testing with sapphire/AlN/MoSi2 samples was carried out to determine film effectiveness as a fiber coating in a composite.

Epitaxial strontium titanate (SrTiO3) thin films have been grown by plasma enhanced metalorganic chemical vapor deposition (PE-MOCVD) technique on different bottom electrode materials, such as Pt/MgO and YBCO/LaAlO3. The as grown SrTiO3 film exhibited an epitaxial structure with <100> orientation perpendicular to the substrates as examined by X-ray diffraction (XRD). The electrical and dielectric properties of the films were investigated by capacitance-voltage (C-V) and current-voltage (I-V) measurements in a temperature range from 80K to 300K. The dielectric constant and dielectric loss were found to be 320 and 0.08 at 100 kHz and room temperature. The dc leakage current density and breakdown voltage were strongly dependent on the choice of the bottom electrode materials. For the films grown on YBCO/LaAlO3, the leakage current density is 8.8×10−7 A/cm2 at 200 kV/cm and the breakdown voltage is about 2.0 MV/cm. These results indicated that the SrTiO3 films are suitable for many devices applications. The frequency dependence of the dielectric constant and dielectric loss were studied in the range of 12 Hz to 1 MHz at room temperature. With the increase of the frequency, the dielectric constant showed a little decrease, while the dielectric loss exhibited a sharp increase which could be attributed to the electrode resistance loss.

Strontium titanate (SrTiO3) thin films have been epitaxially grown on YB2Cu3O7−x (YBCO)/LaAlO3 at substrate temperatures of 660 to 700°C. X-ray diffraction (XRD) results indicated that single crystalline SrTiO3 thin films were epitaxially grown on the substrate with <100> orientation perpendicular to the substrates. The compositions of the films with different growth conditions were examined by Rutherford backscattering spectroscopy (RBS) and energy dispersive x-ray spectroscopy (EDX). The ratio of Sr/Ti is in the range of 0.9 to 1.1 for the films with a thickness of 1000–2000Å. The surface morphology of the films and the interfaces of the SrTiO3/YBCO structure were examined by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Very smooth surface and sharp interface were observed. The superconducting property of the YBCO layer, as measured by ac susceptibility, did not degrade after growth of SrTiO3 film. The dielectric constant as high as 320 was obtained at 100KHz. The leakage current density is less than 1×10−6A/cm2 at 3V operation.

Titanium oxide thin films were deposited at room temperature by the Electron Cyclotron Resonance Plasma-Assisted Chemical Vapor Deposition (ECR-PACVD) method. Effects of deposition temperature, microwave power and plasma gas pressure were investigated. Both Ar and O2 plasma were used to deposit films from titanium isopropoxide (Ti(OC3H7)4) precursor. Transparent titanium oxide films were obtained with O2 plasma. Refractive index and thickness were measured by ellipsometry and the films were characterized by x-ray diffraction.

The objective of this research was to demonstrate heteroepitaxial growth of yttria stabilized cubic zirconia on single crystal silicon substrates by chemical vapor deposition (CVD) using metalorganic source materials. We succeeded in depositing extremely smooth, well aligned films of zirconia on silicon substrates, both the <100> and <111> orientations, without an oxide interfacial layer. Experimental variables investigated included varying zirconia source materials, substrate temperatures, oxygen concentration, gas flow rates, yttria doping, substrate orientation, and cobalt-silicide as an oxygen diffusion barrier. ZrO2 films were predominantly tetragonal when deposited in the absence of oxygen while cubic phase material could be put down at 750°C with oxygen background. Films deposited from TMHD zirconium contained no measurable carbon contamination. Deposits from trifluoro-acetylacetonate Zr contained small amounts of fluorine, even in the presence of water vapor, and some carbon when hydrogen was used as a diluent gas.

Ab initio electronic-structure calculations are combined with empirical bond-additivity corrections to yield thermochemical properties of gas-phase molecules. A self-consistent set of heats of formation for molecules in the Si-H, Si-H-Cl, Si-H-F, Si-N-H and Si-NH- F systems is presented, along with preliminary values for some Si-O-C-H species.