@article{park_sakhrani_maria_cuomo_teng_muth_ware_rodriguez_nemanich_2003, title={Wavelength-dependent Raman scattering of hydrogenated amorphous silicon carbon with red, green, and blue light excitation}, volume={18}, ISSN={["2044-5326"]}, DOI={10.1557/JMR.2003.0106}, abstractNote={This study presents results of wavelength-dependent Raman scattering from amorphous silicon carbon (a-Si:C:H). The a-Si:C:H films were produced by radio-frequency plasma-enhanced chemical vapor deposition. Prior results with amorphous carbon indicate that laser excitation selectively probes clusters with differing sizes. Our measurements with a-Si:C:H indicate that when using red (632.8 nm), green (514.5 nm), and blue (488.0 nm) excitation, the Raman D and G peaks shift to higher wave numbers as the excitation energy increases. The higher frequency is associated with smaller clusters that are preferentially excited with higher photon energy. It appears that photoluminescence occurs due to radiative recombination from intracluster transitions in Si-alloyed sp2-bonded carbon clusters}, number={4}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Park, M and Sakhrani, V and Maria, JP and Cuomo, JJ and Teng, CW and Muth, JF and Ware, ME and Rodriguez, BJ and Nemanich, RJ}, year={2003}, month={Apr}, pages={768–771} }
 @article{park_teng_sakhrani_mclaurin_kolbas_sanwald_nemanich_hren_cuomo_2001, title={Optical characterization of wide band gap amorphous semiconductors (a-Si : C : H): Effect of hydrogen dilution}, volume={89}, ISSN={["1089-7550"]}, DOI={10.1063/1.1332421}, abstractNote={The effect of hydrogen dilution on the optical properties of a wide band gap amorphous semiconductor (a-Si:C:H) was investigated. The samples were prepared by glow discharge decomposition of tetramethylsilane and were characterized primarily by optical techniques: spectroscopic ellipsometry, Raman scattering, infrared absorption, spectrophotometry, and UV photoluminescence. The deposition rate decreased with hydrogen dilution, while the silicon to carbon ratio remained constant with the addition of hydrogen. The optical band gap of this material increased as the hydrogen flow rate increased. Infrared absorption studies show that the concentration of hydrogen which is bonded to carbon decreases systematically upon hydrogen dilution. Hydrogen dilution appears to reduce the size and concentration of sp2 bonded carbon clusters, possibly caused by the etching of sp2 clusters by atomic hydrogen. The result was also supported by the shift of the Raman G peak position to a lower wave number region. Room temperature photoluminescence in the visible spectrum was observed with UV excitation.}, number={2}, journal={JOURNAL OF APPLIED PHYSICS}, author={Park, M and Teng, CW and Sakhrani, V and McLaurin, MB and Kolbas, RM and Sanwald, RC and Nemanich, RJ and Hren, JJ and Cuomo, JJ}, year={2001}, month={Jan}, pages={1130–1137} }
 @article{teng_aboelfotoh_davis_muth_kolbas_2001, title={Photoluminescence and electrical characteristics of the two-dimensional electron gas in Si delta-doped GaN layers}, volume={78}, ISSN={["1077-3118"]}, DOI={10.1063/1.1353836}, abstractNote={We have studied the electrical and photoluminescence (PL) properties of a Si delta-doped GaN layer grown by metalorganic chemical vapor deposition. The Hall mobility and electron sheet concentration are 726 cm2/V s and 1.9×1012 cm−2, respectively, at 2 K. A PL peak located at 78 meV below the band gap of GaN is observed at 77 K. This PL peak is attributed to the radiative recombination between electrons in the two-dimensional quantum states and photoexcited holes in GaN, which is consistent with simulation results using a one-dimensional Poisson and Schrödinger equation solver. The peak disappears at temperatures higher than 77 K and is not observed in uniformly doped GaN layers.}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Teng, CW and Aboelfotoh, MO and Davis, RF and Muth, JF and Kolbas, RM}, year={2001}, month={Mar}, pages={1688–1690} }
 @article{teng_muth_kolbas_hassan_sharma_kvit_narayan_2000, title={Quantum confinement of E-1 and E-2 transitions in Ge quantum dots embedded in an Al2O3 or an AlN matrix}, volume={76}, ISSN={["0003-6951"]}, DOI={10.1063/1.125650}, abstractNote={Alternating layers of Ge quantum dots embedded in either Al2O3 or AlN matrices were deposited on sapphire substrates by pulsed-laser deposition. The characteristics of the dots are shown to be independent of the surrounding matrix. The dots size (73, 130, 160, and 260 ű5%) was controlled by the laser energy density and deposition time, and was characterized by high-resolution transmission electron microscopy. The dots were single crystalline with no apparent GeOx interfacial layers. Transmission spectroscopy at room temperature and 77 K was used to probe the above-band-edge absorption of the Ge nanodots. The spectral positions of both E1/E1+Δ1 and E2 transitions were found to shift to higher energy in the absorption spectra with decreasing nanodot sizes. This indicates that strong quantum-confinement effect permits the optical properties of Ge dots to be modified in a controlled manner.}, number={1}, journal={APPLIED PHYSICS LETTERS}, author={Teng, CW and Muth, JF and Kolbas, RM and Hassan, KM and Sharma, AK and Kvit, A and Narayan, J}, year={2000}, month={Jan}, pages={43–45} }
 @inproceedings{teng_muth_kolbas_hassan_sharma_narayan_2000, title={Quantum confinement of E1 and E2 transitions in Ge quantum dots embedded in Al203 or an AlN matrix}, booktitle={Optical microstructural characterization of semiconductors  (Materials Research Society proceedings, vol. 588)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Teng, C. W. and Muth, J. F. and Kolbas, R. M. and Hassan, K. M. and Sharma, A. K. and Narayan, J.}, editor={J. Piqueras, T. Sekiguchi and Unlu, M. S.Editors}, year={2000} }
 @article{teng_muth_ozgur_bergmann_everitt_sharma_jin_narayan_2000, title={Refractive indices and absorption coefficients of MgxZn1-xO alloys}, volume={76}, ISSN={["0003-6951"]}, DOI={10.1063/1.125912}, abstractNote={Indices of refraction for MgxZn1−xO epitaxial films grown by pulsed-laser deposition on sapphire substrates with x up to 0.36 were determined in the range of wavelength 457–968 nm by analysis of optical transmission spectra and prism-coupled waveguide measurements. The dispersion follows the first-order Sellmeier dispersion equation. Absorption coefficients, exciton energy gaps, and binding energies of MgxZn1−xO alloys were determined by transmission spectroscopy. The excitonic absorption features were clearly visible at room temperature despite alloy broadening. These results provide important information for the design and modeling of ZnO/MgZnO heterostructure optoelectronic devices.}, number={8}, journal={APPLIED PHYSICS LETTERS}, author={Teng, CW and Muth, JF and Ozgur, U and Bergmann, MJ and Everitt, HO and Sharma, AK and Jin, C and Narayan, J}, year={2000}, month={Feb}, pages={979–981} }
 @inproceedings{hassan_sharma_narayan_muth_teng_kolbas_2000, title={Size effect in germanium nanostructures fabricated by pulsed laser deposition}, booktitle={Nanophase and Nanocomposite Materials III  (Materials Research Society proceedings; vol. 581)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Hassan, K. M. and Sharma, A. K. and Narayan, J. and Muth, J. F. and Teng, C. W. and Kolbas, R. M.}, editor={H. Hahn, S. Komarneni and Parker, J. C.Editors}, year={2000} }
 @inproceedings{sharma_jin_narayan_teng_muth_kolbas_holland_2000, title={Structural and optical property investigations on Mg-Alloying in epitaxial zinc oxide films on sapphire}, number={2000}, booktitle={MRS Internet Journal of Nitride Semiconductor Research}, author={Sharma, A. K. and Jin, C. and Narayan, J. and Teng, C. W. and Muth, J. F. and Kolbas, R. M. and Holland, O. W.}, year={2000} }
 @article{sharma_narayan_muth_teng_jin_kvit_kolbas_holland_1999, title={Optical and structural properties of epitaxial MgxZn1-xO alloys}, volume={75}, ISSN={["1077-3118"]}, DOI={10.1063/1.125340}, abstractNote={The optical and structural properties of high-quality single-crystal epitaxial MgZnO films deposited by pulsed-laser deposition were studied. In films with up to ∼36 at. % Mg incorporation, we have observed intense ultraviolet band edge photoluminescence at room temperature and 77 K. The highly efficient photoluminescence is indicative of the excitonic nature of the material. Transmission spectroscopy was used to show that the excitonic structure of the alloys was clearly visible at room temperature. High-resolution transmission electron microscopy, x-ray diffraction, and Rutherford backscattering spectroscopy/ion channeling were used to verify the epitaxial single-crystal quality of the films and characterize the defect content. Post-deposition annealing in oxygen was found to reduce the number of defects and to improve the optical properties of the films. These results indicate that MgZnO alloys have potential applications in a variety of optoelectronic devices.}, number={21}, journal={APPLIED PHYSICS LETTERS}, author={Sharma, AK and Narayan, J and Muth, JF and Teng, CW and Jin, C and Kvit, A and Kolbas, RM and Holland, OW}, year={1999}, month={Nov}, pages={3327–3329} }
 @article{hassan_sharma_narayan_muth_teng_kolbas_1999, title={Optical and structural studies of Ge nanocrystals embedded in AlN matrix fabricated by pulsed laser deposition}, volume={75}, ISSN={["1077-3118"]}, DOI={10.1063/1.124648}, abstractNote={We have fabricated Ge nanostructures buried in a matrix of AlN grown on Si(111) by pulsed laser deposition at the substrate temperature of 500 °C. The characterization of these structures was performed using high-resolution transmission electron microscopy (HRTEM), photoluminescence, and Raman spectroscopy. The HRTEM results show that the Ge islands are single crystal with a pyramidal shape. The average size of Ge islands was determined to be ∼15 nm, which could be varied by controlling laser deposition and substrate parameters. The Raman spectrum showed a peak of the Ge–Ge vibrational mode downward shifted up to 295 cm−1 which is caused by quantum confinement of phonons in the Ge dots. The photoluminescence of the Ge dots (size ∼15 nm) was blueshifted by ∼0.266 eV from the bulk Ge value of 0.73 eV at 77 K, resulting in a distinct peak at ∼1.0 eV. The transmission measurements carried out on different samples having Ge dot sizes of 7, 8, and 13 nm deposited on sapphire substrate showed the above band edge transitions of Ge, which were also blueshifted in accordance with the quantum confinement effect. The importance of pulsed laser deposition in fabricating novel nanostructures is emphasized.}, number={9}, journal={APPLIED PHYSICS LETTERS}, author={Hassan, KM and Sharma, AK and Narayan, J and Muth, JF and Teng, CW and Kolbas, RM}, year={1999}, month={Aug}, pages={1222–1224} }
 @inproceedings{teng_muth_kolbas_hassan_sharma_kvit_narayan_1999, title={Quantum confinement of above-band-bap transitions in Ge quantum dots embedded in an Al2O3 or AIN matrix}, booktitle={Optical microstructural characterization of semiconductors  (Materials Research Society proceedings, vol. 588)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Teng, C. W. and Muth, J. F. and Kolbas, R. M. and Hassan, K. M. and Sharma, A. K. and Kvit, A. and Narayan, J.}, editor={J. Piqueras, T. Sekiguchi and Unlu, M. S.Editors}, year={1999} }
 @inproceedings{hassan_sharma_narayan_muth_teng_kolbas_1998, title={Germanium nanostructures fabricated by pulsed laser deposition}, booktitle={Microcrystalline and nanocrystalline semiconductors--1998: symposium held November 30-December 3, 1998, Boston, Massachusetts, U.S.A.}, author={Hassan, K. M. and Sharma, A. K. and Narayan, J. and Muth, J. F. and Teng, C. W. and Kolbas, R. M.}, year={1998} }