The ferraborane HFe4 (CO)12 BH2 sublimes at 50 °C and decomposes by loss of H2 and CO on various substrate surfaces at 160–180 °C to yield films having metallic appearances with typical thicknesses of 4000Å. These films are amorphous by X-ray, conduct electricity and adhere well to glass, metal and silicon substrates. The composition was determined by ESCA and Auger spectroscopies. The films exhibit highly uniform composition and the Fe/B ratio is 4 showing that film stoichiometry is defined by the cluster core. The ESCA chemical shifts show the presence of boride and metallic iron. At present the bulk film contains a high level of oxygen in the form of iron and boron oxides. No ax-iron is present by X-ray or Mössbauer spectroscopies. Some carbon and hydrogen (SIMS) are present. Mössbauer spectra show the presence of magnetic iron similar to that exhibited by authentic Fe80 B20 samples but the films also contain substantial paramagnetic iron.

ntial catalytic applications [1]. Also, in non-catalytic areas, there is a move to build alloy powders from large metal clusters [2]. Therefore, we have initiated a program to develop intermetallic powders from mixedmetal organometallic precursors [3]. Here we report the synthesis and characterization of iron-cobalt intermetallic powders obtained from heteroorganometallic clusters [4]. Our objective therefore is to (1) provide a simple and effective means of synthesizing iron-cobalt intermetallics (2) vary the ratio of iron to cobalt in such intermetallics, and (3) provide a method to produce homogeneous products from iron-cobalt metalorganic precursors specifically synthesized for this purpose. The resulting intermetallics may have unique magnetic characteristics.

The synthesis of the first soluble silicon-silicon bonded network polymers, the polyalkylsilynes [RSi]n was accomplished using high-intensity ultrasound to effect the reductive condensation of alkyltrichlorosilanes with liquid sodium-potassium alloy. The resulting polymers remain hydrocarbon-soluble and may be cast into transparent films. Spectroscopic data indicate a structure consisting of tetrahedral alkylsilicon units assembled via silicon-silicon bonds into amorphous networks. Films or solutions of the polysilynes exhibit an intense UV absorption which tails into the visible, blue-shifted but similar in shape and intensity to that of amorphous silicon. The photoreactivity and pyrolysis properties of these materials will be described.

Dense silicon carbide films have been prepared by low pressure chemical vapor deposition (LPCVD) using a volatile, heterocyclic, carbosilane precursor, MeHSiCH2SiCH2Me(CH2SiMeH2). At deposition temperatures between 700 and 800° C, polycrystalline, stoichiometric SiC films have been deposited on single crystal silicon and fused silica substrates. Optical microscopy and SEM analyses indicated formation of a transparent yellow film with a uniform, featureless surface and good adherence to the Si(lll) substrate. The results of preliminary studies of the nature of the gaseous by-products of the CVD processes and ultrahigh vacuum physisorption and decomposition of the precursor on Si(100) substrates are discussed.

Chemical vapor deposition from CpCr(CO)3H, Cr(CH2CMe3)4, and Cr(NPri2)3 at low pressures yields chromium carbide films at temperatures as low as 330 °C. The films are mirror-bright and extremely smooth with no significant features observable by SEM. In general, films prepared at higher temperatures had lower resistivities, and were more likely to be crystalline than those prepared at lower temperatures. However, amorphous films deposited at 330 °C were much harder than the crystalline films. Chemical vapor deposition from Cr(NPri2)3 resulted in carbide films with the most desirable properties.

Organometallic aluminum azides have been found to be effective precursors for the low temperature chemical vapor deposition of thin films of aluminum nitride. Quantitative analysis of the gas phase products of the reaction are used to develop an understanding of the reaction. Rate studies of the deposition were performed in the temperature range from 400 to 800°C. Below 525°C, an activation barrier of 26.4 kcal/mol was found, while above 525°C, a value of 5.23 kcal/mol was obtained. The effects of the presence of N-C bonds and the type of Al-N interaction within the precursor are evaluated.

Spray pyrolysis of the mixed metal organometallics, Al[M(CO)3C5H5]3 (M is Cr, Mo or W), prepared in tetrahydrofuran from the mercury analogues and aluminum metal, gave mixed oxide gels on heated alumina substrates. Air was used as the propellant for M = Cr, whereas oxygen was used for M = Mo or W. Mixtures of Al[Cr(CO)3C5 H5]3 and Al(O-i-C3H8)3 having a Cr/Al ratio of 0.02 to 0.93 were used to prepare gels with intermediate dopant concentrations. When calcined at 500 °C, the gels produced amorphous coatings of two-component oxides that were characterized by SEM and EDS methods. The strength of adhesion of a E-beam evaporated chromium metal overlayer to the coating, as measured by a continuous microindentation method, increased in the order Cr < Mo ≅ W; adhesion was found to be directly proportional to the effective free energy of formation of the oxide mixture.

The decomposition of W(CO)6 adsorbed on Si(111)-(7×7) using low energy electrons and ultraviolet photons has been investigated under ultrahigh vacuum conditions. This work is motivated by a desire to understand the mechanism for laser- and electron-assisted chemical vapor deposition (CVD) of tungsten using volatile coordination complexes and to specifically understand the role of the surface in these processes. Both electron stimulated and photo-assisted decomposition of the adsorbed W(CO)6 are observed. No thermal decomposition of the W(CO)6 occurs under the conditions of these experiments, based on independent temperature programmed reaction experiments, ruling out the possibility of laser- or electron-induced heating as the cause of decomposition. Furthermore, the interaction of the W(CO)6 with the Si(111)-(7×7) surface is shown to be exceedingly weak based on the fact that the desorption energy is 9.46 ± 0.77 kcal/mol. Desorption of CO is induced during both ultraviolet photolysis and electron bombardment. Carbon monoxide is exclusively evolved during ultraviolet photolysis: no W-containing fragments are desorbed. During electron bombardment, a small amount of the W(CO)6 is desorbed, accounting for ∼10% of the desorption. In both cases, CO-containing W fragments remain on the surface after decomposition at low surface temperature. The remaining surface fragments do not undergo further photolysis at 308 nm but do react thermally. Competing desorption and dissociation of CO are thermally induced resulting in carbide and oxide impurities in the deposited material. The fact that strongly bound W(CO)x fragments are trapped on the surface is proposed as a limiting factor in the purity of tungsten deposits using the decomposition of W(CO)6.

A systematic study of the origin of contaminants in metal films photochemically deposited from the group VI hexacarbonyls is described. Background gas present in the cell during deposition, exposure to air and incomplctc removal of CO groups from the surface of the growing film all affect C and O incorporation. The data are compared to results of recent experiments examining surface photoproducts of the metal carbonyls.

The one-photon and sequential two-photon KrF* laser (248 nm) photodissociation of Cr(CO)6 and Mo(CO)6 were studied in a molecular beam using mass spectrometry to detect the photoproduct molecular ions. For Cr(CO)6, the major one-photon product, Cr(CO)4, undergoes secondary photodissociation to give predominantly Cr(CO)2. The photodissociation cross section of Cr(CO)4 is found to be 1.6 × higher than that of Cr(CO)6 at 248 nm. For Mo(CO)6, the major one-photon products, Mo(CO)5 and Mo(CO)4, undergo secondary photodissociation to give predominantly Mo(CO)3.

The KrF* (248 nim) laser multiphoton dissociation (MPD) of a series of (arene)chromium tricarbonyls has been investigated in the gas-phase using emission spectroscopy to detect the excited state photoproducts. In the MPD of all compounds studied, chromium atoms are formed in a variety of electronically excited states via a two-channel dissociation mechanism. The predominant pathway for formation of the ground electronic state and the lowest excited states is by a sequential absorption/fragmentation process, where the product of the one-photon dissociation of the parent molecule absorbs an additional photon and dissociates to Cr(I). The higher energy Cr(I) states are formed exclusively by a direct dissociation process, where the parent absorbs multiple photons prior to dissociation. The distribution of excited chromium atoms formed in the direct channel is statistical for all compounds studied and is independent of the nature of the arene ligand. In contrast, the distribution of Cr(I) states formed via the sequential dissociation channel is strongly dependent on the vibrational density of states in the arene ligand.

Optical emission, laser spectroscopic and mass spectrometric techniques have been used to study the ArF excimer laser induced photochemistry of disilane at 193 nm. Evidence is found for the formation of a number of photofragments from single and multiphoton dissociation. Effects due to secondary photolysis are observed at high excimer laser repetition rates.

Films of a- Si: Hwere deposited from Sill4 in a parallel configuration employing acw CO2 laser. Infrared spectra, photoconductivities and dark conductivities of the films were studied as a function of surface temperature between 250°C and400° C. The results are compared with data obtained from deposition experiments using Si2H6 and an ArF laser. Implications for the mechanism of LICVD are discussed.

Steady-state and time resolved molecular beam sampling mass spectrometry have been used to study the ArF excimer laser induced photochemistry of silaneammonia mixtures at 193 nm. Under both steady state and single laser shot conditions, products as complicated as tetraaminosilane are formed promptly. A mechanism which accounts for the formation of all observed products is proposed and evaluated.

Amorphous silica films deposited from the mixture of gases (Si2 H6 and Si2F6) by deutrium-lamp CVD were studied by IR, vacuum UV, EPR and Auger electron (AE) spectrometries. The F-doping enhanced the film growth and removed defects in the film such as -H, -OH, and E' centers. A model on deposition and defect formation mechanisms was proposed based on the thermodynamic Stabilities of resultant HF in the reactions. The AES study showed that the film surface modified by activated oxygen had an increased hardness against electron beams.

The direct photo-CVD of silicon dioxide on c-Si substrates has been achieved using a new combination of Si2H6 and N2O3 gases, with an external deuterium lamp as the VUV source. The variation of the deposition rate and the refractive index with process parameters is reported. FTIR studies on these oxides show that the oxide is very nearly stoichiometric with no Si-N bonds and only trace amounts of Si-H bonds. C-V, I-V and breakdown measurements made on these films are reported. a-Si:H thin film transistors have also been fabricated using this oxide as the gate dielectric.

High-purity digermane (Ge2H6, 5% in He) has been used to grow epitaxially oriented crystalline Ge films by pyrolysis. Amorphous Ge:H films also have been deposited by pyrolysis and ArF (193 nm) laser-induced photolysis. The amorphous-to-crystalline transition and the film's morphology was studied as a function of deposition conditions. The film's microstructure, strain and epitaxial quality were assessed using x-ray diffraction curves and scanning and transmission electron microscopy. It was found that commensurate, coherently strained epitaxial Ge films could be grown pyrolytically on (100) GaAs at low (0.05–40 m Torr) Ge2H6 partial pressures, for substrate temperatures above 380°C.

Studies of the unimolecular decay, following the excitation of core electrons of the carbon and fluorine atoms in carbon tetrafluoride and silicon and fluorine in silicon tetrafluoride by monochromatic, synchrotron radiation, provided evidence for a “valence bond depopulation” fragmentation mechanism. The fragmentation processes were examined using time-of flight mass spectroscopy. The mass spectra show the distribution of ions collected in coincidence with low and high energy electrons. Distinct changes in the mass spectra with atomic site of excitation and photon energy are observed. The observation of F2+ ions in the time-of-flight mass spectra following excitation of a fluorine is electron in SiF4 is significant because it provides direct evidence for the formation of a localized, two-hole, final valence state that persists on the time scale of fragmentation. In contrast, the lack of F2+ ions from CF4, indicates that the fragmentation occurs through a delocalized two-hole state.

The chtaracteristics of ion beam assisted deposition are discussed and compared with those of photon beam assisted deposition. Effects of various deposition parameters including ion species, beam energy and substrate temperature are discussed. Deposited films usually include impurities such as C and O. Inclusion of oxygen takes place by enhanced oxidation by background oxygen and may be reduced by depositing in a clean vacuum. Promising applications of maskless ion beam assisted deposition are also discussed.

A process for repair of micron and submicron sized transparent defects on photomasks is described. Opaque films are deposited at the intersection of the flux of organic monomers from a gas jet and a 20 keV Ga ion beam. Focused ion beam-induced deposition differs from other ion-induced, electron beam and laser processes due to the very high ion current density and the sputtering of the material as it is being deposited. We have explored the deposition-sputtering rate competition for several precursor materials as a function of monomer flux and ion beam dose rate. Our results suggest a model for deposition which requires polymerization of the precursor through carbon-carbon double bonds to favor deposition over sputtering by creating high molecular weight material at the target.