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Transient surface photovoltage studies of bare and Ni-filled porous silicon performed in different ambients.

Granitzer P, Rumpf K, Strzhemechny Y, Chapagain P - Nanoscale Res Lett (2014)

Bottom Line: The resulting pores were oriented towards the surface with an average pore diameter of 60 nm and the thickness of the porous layer of approximately 40 μm.SPV was performed on a bare porous silicon as well as on a Ni-filled porous silicon in vacuum and in different gaseous environments (O2, N2, Ar).A significant difference was observed between the 'light-on' and 'light-off' SPV transients obtained in vacuum and those observed in gaseous ambiences.

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Affiliation: Institute of Physics, Karl Franzens University Graz, Universitaetsplatz 5, Graz, 8010, Austria.

ABSTRACT

Unlabelled: Mesoporous silicon and porous silicon/Ni nanocomposites have been investigated in this work employing light-dark surface photovoltage (SPV) transients to monitor the response of surface charge dynamics to illumination changes. The samples were prepared by anodization of a highly n-doped silicon wafer and a subsequent electrodepositing of Ni into the pores. The resulting pores were oriented towards the surface with an average pore diameter of 60 nm and the thickness of the porous layer of approximately 40 μm. SPV was performed on a bare porous silicon as well as on a Ni-filled porous silicon in vacuum and in different gaseous environments (O2, N2, Ar). A significant difference was observed between the 'light-on' and 'light-off' SPV transients obtained in vacuum and those observed in gaseous ambiences. Such behavior could be explained by the contribution to the charge exchange in gas environments from chemisorbed and physisorbed species at the semiconductor surface.

Pacs: 81.05.Rm; 73.20.-r; 75.50.-y; 82.45.Yz.

No MeSH data available.


SPV transients in gaseous environments. (a) Bare PS in N2. (b) Ni-filled PS in O2.
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Figure 2: SPV transients in gaseous environments. (a) Bare PS in N2. (b) Ni-filled PS in O2.

Mentions: SPV transients for both types of samples in different gases show anomalous spikes of SPV during both ‘light-on’ and ‘light-off’ events (Figure 2). Similar behavior is observed for all three gaseous environments. After obtaining the SPV transients in these gas ambients, the experimental chamber was evacuated and then the SPV transients were obtained in vacuum.As a result, we observed that the PS surface was very sensitive to the experimental ambient, as one can see from Figure 3. In vacuum, the sharp SPV spikes disappeared whereas the light-on and light-off saturation times became dissimilar. Resolving the SPV transients obtained in gaseous environments on the logarithmic time scale (cf. Figure 4), one can see that these curves contain both fast and slow components with opposite contributions to charge dynamics. The initial fast process in the case of light-on and light-off events in the gaseous environments occurs over a time scale of tens of seconds, whereas the entire event until saturation is in the range of thousands of seconds. However, the transients observed in vacuum revealed only one relatively fast process. Since the fast process is always present regardless of the ambient conditions, we believe that it is related to the charge recombination occurring in PS. On the other hand, the slow process is present only in the gaseous environments suggesting that it might be related to the non-vacuum ambient.


Transient surface photovoltage studies of bare and Ni-filled porous silicon performed in different ambients.

Granitzer P, Rumpf K, Strzhemechny Y, Chapagain P - Nanoscale Res Lett (2014)

SPV transients in gaseous environments. (a) Bare PS in N2. (b) Ni-filled PS in O2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4155768&req=5

Figure 2: SPV transients in gaseous environments. (a) Bare PS in N2. (b) Ni-filled PS in O2.
Mentions: SPV transients for both types of samples in different gases show anomalous spikes of SPV during both ‘light-on’ and ‘light-off’ events (Figure 2). Similar behavior is observed for all three gaseous environments. After obtaining the SPV transients in these gas ambients, the experimental chamber was evacuated and then the SPV transients were obtained in vacuum.As a result, we observed that the PS surface was very sensitive to the experimental ambient, as one can see from Figure 3. In vacuum, the sharp SPV spikes disappeared whereas the light-on and light-off saturation times became dissimilar. Resolving the SPV transients obtained in gaseous environments on the logarithmic time scale (cf. Figure 4), one can see that these curves contain both fast and slow components with opposite contributions to charge dynamics. The initial fast process in the case of light-on and light-off events in the gaseous environments occurs over a time scale of tens of seconds, whereas the entire event until saturation is in the range of thousands of seconds. However, the transients observed in vacuum revealed only one relatively fast process. Since the fast process is always present regardless of the ambient conditions, we believe that it is related to the charge recombination occurring in PS. On the other hand, the slow process is present only in the gaseous environments suggesting that it might be related to the non-vacuum ambient.

Bottom Line: The resulting pores were oriented towards the surface with an average pore diameter of 60 nm and the thickness of the porous layer of approximately 40 μm.SPV was performed on a bare porous silicon as well as on a Ni-filled porous silicon in vacuum and in different gaseous environments (O2, N2, Ar).A significant difference was observed between the 'light-on' and 'light-off' SPV transients obtained in vacuum and those observed in gaseous ambiences.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Physics, Karl Franzens University Graz, Universitaetsplatz 5, Graz, 8010, Austria.

ABSTRACT

Unlabelled: Mesoporous silicon and porous silicon/Ni nanocomposites have been investigated in this work employing light-dark surface photovoltage (SPV) transients to monitor the response of surface charge dynamics to illumination changes. The samples were prepared by anodization of a highly n-doped silicon wafer and a subsequent electrodepositing of Ni into the pores. The resulting pores were oriented towards the surface with an average pore diameter of 60 nm and the thickness of the porous layer of approximately 40 μm. SPV was performed on a bare porous silicon as well as on a Ni-filled porous silicon in vacuum and in different gaseous environments (O2, N2, Ar). A significant difference was observed between the 'light-on' and 'light-off' SPV transients obtained in vacuum and those observed in gaseous ambiences. Such behavior could be explained by the contribution to the charge exchange in gas environments from chemisorbed and physisorbed species at the semiconductor surface.

Pacs: 81.05.Rm; 73.20.-r; 75.50.-y; 82.45.Yz.

No MeSH data available.