Papers by Author: Robert P. Devaty

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Authors: Yue Ke, Catherine Moisson, S. Gaan, R.M. Feenstra, Robert P. Devaty, Wolfgang J. Choyke
Abstract: The effects of initial surface morphology on the early stages of porous SiC formation under highly biased photoelectrochemical etching conditions are discussed. We etched both Si-face and C-face polished n-type 6H SiC with different surface finishes prepared either by mechanical polishing or by chemical mechanical polishing at NOVASiC. For both Si-face and C-face porous SiC samples, a variety of surface and cross sectional porous morphologies, due to different surface finishes, are observed. The proposed explanation is based on the spatial distribution of holes at the interface of the SiC and electrolyte inside the semiconductor.
Authors: Y. Shishkin, Yue Ke, Robert P. Devaty, Wolfgang J. Choyke
Abstract: A brief historical development of porous SiC and GaN is given. SEM images of nine porous morphologies in 4H, 6H and 3C SiC are shown along with anodization details. Similarly, two porous GaN morphologies are presented. Applications and future prospects are discussed.
Authors: T. Hornos, Adam Gali, Robert P. Devaty, Wolfgang J. Choyke
Abstract: Ab initio supercell calculations have been carried out to investigate the doping of phosphorus in chemical vapor deposited (CVD) SiC layers. CVD conditions have been simulated by using the appropriate chemical potentials for hydrogen and phosphorus (P). We found that the most abundant defect is P at Si-site followed by P at C-site. The calculated concentrations of the P-donors and free carriers in CVD grown SiC agree with the experimental results.
Authors: S.G. Sridhara, Song Bai, O. Shigiltchoff, Robert P. Devaty, Wolfgang J. Choyke
Authors: Walter M. Klahold, Robert P. Devaty, Wolfgang J. Choyke, Koutarou Kawahara, Tsunenobu Kimoto, Takeshi Ohshima
Abstract: Ultra-pure n-type (8×1013 cm-3), 99 μm thick epitaxial films of 4H SiC were electron irradiated at 170 keV with a fluence of 5×1016 cm-2 or at 1 MeV with a fluence of 1×1015 cm-2 in various geometries. Low temperature photoluminescence (LTPL) spectra and microwave photoconductance (μPCD) lifetime measurements were obtained on all samples prior to annealing and after annealing in Argon in free standing mode or on a POCO carbon platform, every 50°C from 1100°C to 1500°C. No improvement in carrier lifetime was obtained. Spurious lines attributable to the use of a Genesis CX 3550Å laser are also reported.
Authors: S.G. Sridhara, D.G. Nizhner, Robert P. Devaty, Wolfgang J. Choyke, T. Troffer, Gerhard Pensl, David J. Larkin, H.S. Kong
Authors: G.T. Andrews, Maynard J. Clouter, B. Mroz, Y. Shishkin, Yue Ke, Robert P. Devaty, Wolfgang J. Choyke
Authors: G.T. Andrews, C.K. Young, A. Polomska, Maynard J. Clouter, Yue Ke, Robert P. Devaty, Wolfgang J. Choyke
Abstract: Brillouin spectra have been recorded for a series of supported films of p-type porous 6H-SiC with a branched morphology and porosities in the range from 30% to 58%. Complex spectra comprising up to 7 identifiable components were observed in some cases. An effective medium model is being developed as an aid in interpreting the spectra, and preliminary results are presented.
Authors: A.J. Rosenbloom, S. Nie, Yue Ke, Robert P. Devaty, Wolfgang J. Choyke
Abstract: We present relative recovery data for six proteins diffusing through porous silicon carbide membranes having a hybrid columnar/dendritic morphology. These membranes are promising candidates for implantable biosensors. The results are interpreted using an effective medium model.
Authors: Yue Ke, Fei Yan, Robert P. Devaty, Wolfgang J. Choyke
Abstract: A hybrid columnar and dendritic porous structure has been developed in n-type 6H SiC using photoelectrochemical etching with proper control of the applied voltage and current density. The diameter of the formed columnar pores is around 200-500 nm. A possible formation mechanism due to the spatial distribution of holes and the HF concentration gradient in the pores is proposed. A self-supporting film with this morphology is a promising candidate for protein dialysis.
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