Natale J. Ianno

Fabrication of n-type nickel doped B5C1+δ homojunction and heterojunction diodes

We have successfully nickel doped a boron carbide (B5C) alloy film. The nickel doped boron-carbide (Ni-B5C1+δ) thin films were fabricated from a single source carborane cage molecule and nickelocene [Ni(C5H5)2] using plasma enhanced chemical vapor deposition. Nickel doping transforms the highly resistive undoped film from a p-type material to an n-type material. This has been verified from the characteristics of diodes constructed of Ni-B5C1+δ on both n-type silicon and p-type B5C. The homojunction diodes exhibit excellent rectifying properties over a wide range of temperatures.

Fabrication of boron-carbide boron heterojunction devices

We have succeeded in the fabrication of a boron–carbide/boron diode on an aluminum substrate, and a boron–carbide/boron junction field effect transistor. Our results suggest that with respect to the approximately 2 eV band gap pure boron material, 0.9 eV band gap boron–carbide (B5C) acts as a p‐type material. Both boron and boron–carbide (B5C) thin films were fabricated from single source borane cage molecules using plasma enhanced chemical vapor deposition (PECVD). Epitaxial growth does not appear to be a requirement.

Single‐Step Formation of Graphene on Dielectric Surfaces

The direct formation of graphene on various dielectric surfaces is successful via a single-step rapid thermal processing (RTP) of substrates coated with amorphous carbon (C) and nickel (Ni) thin films. High-quality graphene is obtained uniformly on the whole surface of wafers with a controlled number of graphene layers. The monolayer graphene exhibits a low sheet resistance and a high optical transmittance in the visible range.

Heterojunction fabrication by selective area chemical vapor deposition induced by synchrotron radiation

We have fabricated a B5C, boron‐carbide/Si(111) heterojunction diode by the synchrotron radiation‐induced decomposition of orthocarborane. This diode can be compared with similar boron‐carbide/Si(111) heterojunction diodes fabricated by plasma enhanced chemical vapor deposition. The synchrotron radiation induced chemical vapor deposition is postulated to occur via the decomposition of weakly chemisorbed species and the results suggest that ‘‘real‐time’’ projection lithography (selective area deposition) of boron‐carbide devices is possible.

Comparison of different chemical vapor deposition methodologies for the fabrication of heterojunction boron-carbide diodes

Abstract We find that boron-carbide thin film diodes are insensitive to the morphology of the film. The semiconductor properties of the material do not appear to depend upon crystallite size and the extent of long range order. Boron-carbide diodes were fabricated from a single source compound, closo-1,2-dicarbadodecaborane (C 2 B 10 H 12 ), and binary source gases, nidopentaborane (B 5 H 9 ) and methane (CH 4 ). Closo-1,2-dicarbadodecaborane was used in both synchrotron radiation induced chemical vapor deposition (SR-CVD) and plasma enhanced chemical vapor deposition (PECVD) to form boron-carbide films on n-type Si(111). A nidopentaborane and methane combination was also used in PECVD to form boron-carbide films on similar substrate for comparison. All of these boroncarbide films formed similar heterojunction diodes with n-type Si(111).

Recent developments in spectroscopic ellipsometry for in situ applications

The in situ measurement capabilities and advantages of recently developed spectroscopic ellipsometry (SE) instrumentation, which covers wide spectral ranges (190-1700 nm, or 0.73-6.5 eV) and is based on rotating-compensator technology, are described. A technique which can quantitatively correct for window birefringence is presented. Current in situ SE deposition monitoring and control applications in the compound semiconductor, display, and optical coatings industries are also presented.

Combined optical and acoustical method for determination of thickness and porosity of transparent organic layers below the ultra-thin film limit

Analysis techniques are needed to determine the quantity and structure of materials composing an organic layer that is below an ultra-thin film limit and in a liquid environment. Neither optical nor acoustical techniques can independently distinguish between thickness and porosity of ultra-thin films due to parameter correlation. A combined optical and acoustical approach yields sufficient information to determine both thickness and porosity. We describe application of the combinatorial approach to measure single or multiple organic layers when the total layer thickness is small compared to the wavelength of the probing light. The instrumental setup allows for simultaneous in situ spectroscopic ellipsometry and quartz crystal microbalance dynamic measurements, and it is combined with a multiple-inlet fluid control system for different liquid solutions to be introduced during experiments. A virtual separation approach is implemented into our analysis scheme, differentiated by whether or not the organic adsorbate and liquid ambient densities are equal. The analysis scheme requires that the film be assumed transparent and rigid (non-viscoelastic). We present and discuss applications of our approach to studies of organic surfactant adsorption, self-assembled monolayer chemisorption, and multiple-layer target DNA sensor preparation and performance testing.

Optical properties of boron carbide (B5C) thin films fabricated by plasma‐enhanced chemical‐vapor deposition

Variable angle of incidence spectroscopic ellipsometry was used to determine the optical constants near the band edge of boron carbide (B5C) thin films deposited on glass and n‐type Si(111) via plasma‐enhanced chemical‐vapor deposition. The index of refraction n, the extinction coefficient k, and the absorption coefficient are reported in the photon energy spectrum between 1.24 and 4 eV. Ellipsometry analysis of B5C films on silicon indicates a graded material, while the optical constants of B5C on glass are homogeneous. Line shape analyses of absorption data for the films on glass indicate an indirect transition at approximately 0.75 eV and a direct transition at about 1.5 eV.Variable angle of incidence spectroscopic ellipsometry was used to determine the optical constants near the band edge of boron carbide (B5C) thin films deposited on glass and n‐type Si(111) via plasma‐enhanced chemical‐vapor deposition. The index of refraction n, the extinction coefficient k, and the absorption coefficient are reported in the photon energy spectrum between 1.24 and 4 eV. Ellipsometry analysis of B5C films on silicon indicates a graded material, while the optical constants of B5C on glass are homogeneous. Line shape analyses of absorption data for the films on glass indicate an indirect transition at approximately 0.75 eV and a direct transition at about 1.5 eV.

Preparation of high Tc Tl‐Ba‐Ca‐Cu‐O thin films by pulsed laser evaporation and Tl2O3 vapor processing

Tl‐Ba‐Ca‐Cu‐O superconducting thin films with zero‐resistance temperatures up to 115 K have been prepared using a Tl2 O3 vapor process on Ba‐Ca‐Cu‐O precursor thin films. The Ba‐Ca‐Cu‐O thin films were made by laser deposition on Y‐stabilized ZrO2 substrates. This technique minimizes problems caused by the toxicity of Tl2 O3, and its subsequent decomposition to the volatile and toxic Tl2 O upon heating. Therefore, it may have practical application in the fabrication of high Tc Tl‐Ba‐Ca‐Cu‐O superconducting thin‐film devices.

Preparation of high T/sub c/ Tl-Ba-Ca-Cu-O thin films by pulsed laser evaporation and Tl/sub 2/O/sub 3/ vapor processing

Tl‐Ba‐Ca‐Cu‐O superconducting thin films with zero‐resistance temperatures up to 115 K have been prepared using a Tl2 O3 vapor process on Ba‐Ca‐Cu‐O precursor thin films. The Ba‐Ca‐Cu‐O thin films were made by laser deposition on Y‐stabilized ZrO2 substrates. This technique minimizes problems caused by the toxicity of Tl2 O3, and its subsequent decomposition to the volatile and toxic Tl2 O upon heating. Therefore, it may have practical application in the fabrication of high Tc Tl‐Ba‐Ca‐Cu‐O superconducting thin‐film devices.