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3 Acta Physica Polonica A

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Mechanical and Electrical Properties, of ZnO-Nanowire/Si-Substrate Junctions Studied by Scanning Probe Microscopy

100%

Aleszkiewicz M. , Fronc K. , Wróbel J. , Klepka M. , Wojtowicz T. , Karczewski G.

Acta Physica Polonica A

2007

tom 112

nr 2

255-260

Scanning tunneling spectroscopy was used to check the tunneling I-V characteristics of junctions formed by n-ZnO nanowires deposited on Si substrates with n- and p-type electrical conductivity (i.e. n-ZnO nanowire/n-Si and n-ZnO nanowire/p-Si junctions, respectively). Simultaneously, several phenomena which influence the measured I-V spectra were studied by atomic force microscopy. These influencing factors are: the deposition density of the nanowires, the possibility of surface modification by tip movement (difference in attraction forces between nanowires and the p-Si and n-Si) and the aging of the surface.

Low-Frequency Raman Spectrum οf Bulk Zn_{0.984}Co_{0.016}O Crystal

84%

Szuszkiewicz W. , Łusakowski A. , Morhange J. , Gołacki Z. , Arciszewska M. , Brodowska B. , Kanehisa M. , Klepka M. , Dobrowolski W.

Acta Physica Polonica A

2009

tom 116

nr 1

103-106

The influence of possible presence of Co^{2+} ion pairs in a bulk Zn_{1-x}Co_{x}O mixed crystal on the low-frequency part of the Raman spectrum is discussed. Two effects can be taken into account in the theoretical considerations when analyzing the energy level scheme corresponding to Co ions. The first is a local lattice deformation in the vicinity of Co^{2+} ion due to a presence of the second ion, smaller than the host ZnO lattice cation. Such deformation creates a trigonal field, which can only slightly modify the energy levels of Co^{2+} ion. The second effect, which results from an antiferromagnetic superexchange interaction between two Co^{2+} ions is responsible for a new set of energy levels. The Raman data taken at low temperature on the sample corresponding to the composition x = 0.016 demonstrated the presence of two structures at about 6 cm^{-1} and 13 cm^{-1}. These structures may be interpreted as electronic transitions between the ground state and the first excited state of a single Co^{2+} ion in the substitution site of ZnO lattice and as a similar transition for Co^{2+} ion pair, respectively.

Photoluminescence Properties of ZnO and ZnCdO Nanowires

67%

Zaleszczyk W. , Fronc K. , Aleszkiewicz M. , Paszkowicz W. , Wróbel J. , Dłużewski P. , Kret S. , Klepka M. , Kłopotowski Ł. , Karczewski G. , Wojtowicz T.

Acta Physica Polonica A

2007

tom 112

nr 2

357-362

We report on the photoluminescence studies of ZnO and ZnCdO nanowires grown on SiO_2/Si substrates by low-pressure vapor phase synthesis. X-ray diffraction and transmission electron microscopy measurements show that the crystallographic structure of these ZnO and ZnCdO nanowires is of wurtzite-type with a high crystal perfection. Surface morphology of samples was determined by scanning electron microscopy and atomic force microscopy. The photoluminescence spectra of as-grown nanowires, nanowires extracted from the substrate and deposited onto Si wafer, and nanowires dispersed in ethanol by sonication were investigated at room temperature and compared to each other. The temperature dependence of the near band-gap photoluminescence emitted by the as-grown nanowires was also measured and analyzed.