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Influence of the second shell layer (TOPO, HDA) on the optical properties of CdSe/ZnS nanocrystal powder

Zatryb G., Podhorodecki A., Misiewicz J., Nauka K.

Optica Applicata

2007

Vol. 37, nr 4

459-464

CdSe/ZnS nanocrystal powder covered with an additional cap layer (II-shell) of hexadecylamine (HDA) or tri-n-octylphosphine oxide (TOPO) has been investigated by using photoluminescence (PL) and total photoluminescence excitation (TPLE) spectroscopy. Depending on II-shell composition, different emission properties of the system have been observed. Strong emission bands at 2.00 eV and 1.95 eV related to nanocrystalline CdSe core recombination have been observed for TOPO and HDA-CdSe/ZnS nanocrystals, respectively. In both cases, weak emission bands centered at 3.5 and 2.8 eV have also been found. Moreover, in the case of TOPO II-shell, emission band at 1.65 eV related to defect state recombination has been observed. In both cases, similar absorption properties have been found, indicating that II-shell composition does not change nanocrystal absorption properties in an efficient way.

Surface photovoltage in silicon: novel applications for chemical and biological sensing

Nauka K., Li Z., Kamins T. I.

Materials Science Poland

2005

Vol. 23, No. 3

653--661

The Surface Photovoltage technique has been recently employed for chemical and biological sensing. Selected chemical and biological species deposited on the crystalline silicon surface introduced surface barrier changes that were detected using the non-contact Surface Photovoltage mode. The magnitude of the surface barrier modifications provided a unique signature of the sensed species. The simplicity and sensitivity of this technique offer an exciting opportunity for a new type of low cost sensing devices.

Photoreflectance spectroscopy of strained Si1-xGex/Si epilayers

Sitarek P., Misiewicz J., Nauka K.

Electron Technology

1998

Vol. 31, No. 3/4

409-410

Si1-xGex epilayers with germanium composition up to 25% have been studied by photoreflectance spectroscopy. All sprectra were obtained at room temperature with He-Ne laser as the pumping source. Aspne's analytical formula applied to the PR spectra allowed us to determine the optical transtion energies. The observed transitions were identified as E1 and E'0 ( E1+∆1) direct transitons at Si1-xGex layers were analyzed in terms of the changes of the optical transition energies comparing to unstrained material.