Institutional repository of Taras Shevchenko National University of Kyiv eKNUTSHIR
Not a member yet
15422 research outputs found
Sort by
Structure and optical parameters of the system with porous silicon: ellipsometric study
No full textThe prmcipal angle-of-incidence and effipticity tgp ofthe light reflected from PS surface are measured in the visible on two samples by spectroellipsometry methods. The dependence of the reflected light intensity in the s-plane and ellipsometric parameters on the angle-of-incidence and photoluminescence spectra excited by a pulsed nitrogen laser are recorded as well. An increase of the photoluminescence intensity in storing the sample in the atmosphere and corresponding change of the chipsometric curves are detected. The obtained evidence indicate the formation of a two-layer structure during electrochemical etching of silicon, the outer layer being transparent and supposedly consisting of silicon compound with nanociystalline silicon residuals, while the inner one being the layer ofporous silicon whose pores are filled with the same compound. Assuming that the compound is silicon dioxide, we have determined the fraction ofsilicon in the outer layer. The layer refraction index and thickness are determined. It is established that the photoluminescence is more intense in the sample regions with thicker outer layer.Фізичний факультет Київського національного університету імені Тараса Шевченк
Light-activated photoluminescence of porous silicon
No full textSamples ofporous silicon (PS) were etched in concentrated hydrofluonc acid. The initial and etched samples were exposed to the air by pairs at room temperature either in the dark or in daylight. In the process of exposition the integrated intensity of photoluminescence (IPL) excited by a nitrogen laser (337 nm) was measured in regular time intervals on all samples. It has been established that when samples are exposed to the light their 'PL rises with lime, increasing more rapidly in the etched samples than in the nonetched ones. 'PL of the etched samples flattened out after several weeks, while that of the nonetched ones — after several months. 'PL ofthe samples that were in the dark practically did not change with time. It is shown that the rate of 'PL nse depends on a degree of ionization of the air where the samples were located. The results obtained confirm the idea that one ofthe main factors limiting the quantum yield of PS photolurninescence is the nonradiative recombmation that results from the presence ofdangling bonds which may be saturated by the light-generated air ions.Фізичний факультет Київського національного університету імені Тараса Шевченк