Peter A. Dowben

Characterization of boron carbide thin films fabricated by plasma enhanced chemical vapor deposition from boranes

We have fabricated boron carbide thin films on Si(111) and other substrates by plasma‐enhanced chemical‐vapor deposition (PECVD). The PECVD of boron carbides from nido‐cage boranes, specially nido‐pentaborane(9) (B5H9), and methane (CH4) is demonstrated. The band gap is closely correlated with the boron to carbon ratio and can range from 0.77 to 1.80 eV and is consistent with the thermal activation barrier of 1.25 eV for conductivity. We have made boron carbide by PECVD from pentaborane and methane that is sufficiently isotropic to obtain resistivities as large as 1010 Ω cm at room temperature. This material is also shown to be suitable for photoactive p‐n heterojunction diode fabrication in combination with Si(111).

Final-state symmetry effects in photoemission of thin Gd overlayers

The 4f valence band and shallow core levels of ultrathin Gd overlayers on Cu(100) and on crystalline nickel overlayers on Cu(100) have been investigated using angle-resolved photoemission. The authors have observed a definite selection of final-state symmetries which, for one-half to four-monolayer-thick Gd films, indicates that the occupied Gd 5d band is predominantly 3z2-r2 and j=3/2 in character. The 5p3/2 appears to be predominantly z in character for thin Gd overlayers on Cu(100). This occurs as a consequence of final-state interactions between the Gd5d and 5p eigenstates. These results, together with the observed screening processes of the photoemission hole state, are discussed and applied to the understanding of photoemission resonance from the valance bands.

Selective area deposition of boron on Si(111) induced by synchrotron radiation

We have performed the first deposition of boron on Si(111) induced by broadband synchrotron radiation (SR). Contamination‐free thin films were grown at room temperature using decaborane (B10H14) as the source gas. After deposition the films were examined using photoelectron microscopy, which showed that film growth was limited to the region illuminated by SR. The temperature of the substrate rose less than 10 K. These results indicate that gas‐phase excitations are not important and that the films are deposited by a nonthermal, photoinduced mechanism. Masked exposures demonstrate the potential of this technique for patterned deposition.

Iron and nickel thin film deposition via metallocene decomposition

Abstract We demonstrate that iron and nickel thin films can be produced by pyrolysis of ferrocene and nickelocene respectively. These thin films adhere very well to steel and nickel substrates. Analysis of available thermodynamic data suggests that plasma deposition and photoassisted deposition of iron and nickel from their metallocenes is energetically feasible. Thermodynamic Born-Haber cycles illuminating the gaseous decomposition of ferrocene, nickelocene and cobaltocene are presented.

Angle-resolved photoemission evidence for a Gd(0001) surface state

Abstract From angle resolved photoemission we have observed a surface state on Gd(0001) near the Fermi energy in the vicinity of Γ in agreement with a recently calculated band structure. This surface state is of prominent character (Δ 1 ) at Γ . The observation of this surface state can be correlated with the development of the gadolinium bulk band structure which occurs with increasing film thickness as gadolinium films are grown on W(110).

Deposition of thin metal and metal silicide films from the decomposition of organometallic compounds

Abstract The deposition of metal silicide thin films can be undertaken using volatile organometallic complexes. Organometallic vapor phase epitaxy or metal-organic chemical vapor phase epitaxy has a number of potential advantages over conventional chemical vapor deposition and molecular beam epitaxy technologies, and a number of novel thin film materials may be made from organometallic compounds. Plasma-, pyrolytic- and photolytic- assisted decomposition of organometallic complexes have been undertaken in an effort to make a variety of metallic and metal silicide thin films. These efforts are comprehensively reviewed.

CHROMIUM OXIDE FILMS FABRICATED BY CR(CO)6 CHEMICAL VAPOR DEPOSITION

Abstract Cr2O3 and ferromagnetic chromium dioxide have been fabricated by ultraviolet photolytic and plasma-assisted decomposition of Cr(CO)6 in oxygen carrier gas. The photolysis process is surface mediated and proceeds by the sequential removal of (CO) groups. It yields different surface morphologies, and control of the substrate temperature is essential for optimum results. The plasma-assisted deposited films exhibit long-range ferromagnetic order and sufficient flatness to be utilized as a magneto-optic recording medium. The thermodynamic cycle of the plasma process was determined. Consequences for using such films are discussed.

Synchrotron-radiation-induced deposition of boron and boron carbide films from boranes and carboranes: Decaborane

Boron has been deposited successfully on Si(111) from the synchrotron‐radiation‐induced decomposition of decaborane (14), i.e., B10H14. The rate of deposition is limited by the adsorption rate of decaborane (14) on the surface. In addition there is some indication that there is an activation barrier to dissociative adsorption. The synchrotron‐radiation‐ induced growth rate of boron thin films from decaborane (14) is linear with coverage for a large range of thickness, suggesting a constant sticking coefficient for decaborane adsorption at room temperature.

Patterned photoassisted organometallic deposition of iron, nickel and palladium on silicon

Description de la photodeposition des metaux a partir de metallocenes et especes similaires. Analyse par microscopie electronique a balayage et spectrometrie dispersive de la microstructure et de la morphologie des depots

Synchrotron-radiation-induced deposition of boron and boron carbide films from boranes and carboranes II: Nido-2,3-diethyl-2,3-dicarbahexaborane

Boron-carbon thin films have been successfully deposited on Si (111) from the synchrotron radiation induced decomposition of the nido-2,3-diethyl-dicarbahexaborane, (CH3CH2)2C2B4H6. There are indications that molecular precursor states to complete dissociation exist, and that dissociation is the rate limiting step. As with deposition of boron from decaborane, there is an activation barrier to dissociation of diethylcarborane on Si (111). The composition of the growing film, as determined by the boron to carbon ratio, is strongly dependent upon the boron concentration at the surface of the substrate. The boron concentration of the film increases with increasing film thickness.