Influence of adsorbed oxygen on the surface photovoltage and photoluminescence of ZnO nanorods

Abstract

ZnO nanorods have been prepared with sol–gel methods using zinc acetate dihydrate in ethanol in the presence of lithium hydroxide via alkaline hydrolysis. The electron transfer behaviour at the surface and interface in ZnO nanorods was investigated by means of the surface photovoltage technique. The influence of adsorbed oxygen on the surface photovoltage (SPV) response of ZnO nanorods was studied by surface photovoltage spectroscopy (SPS) and field-induced surface photovoltage spectroscopy (FISPS). The results of SPS demonstrate that for ZnO nanorods the built-in electric field should be a main driving force for the separation of the photogenerated electron–hole pairs and its ensuing SPV response. The method of photogenerated charge recombination was also studied with the aid of PL spectroscopy. It is shown that the two methods of energy relaxation in light-excited ZnO nanorods are competitive. When oxygen is adsorbed at the surface and the built-in electric field is formed, the SPV response should be the leading one. Nevertheless, when oxygen is absent, the energy relaxation is mostly carried out by radiative emission.

Electrical analysis of individual ZnO nanowires

“…If there is additional oxygen or some other negative charge molecules on the surface, then band bending and state pinning would take place. 17 Then electrons require higher excitation energy, yielding a reduction of mobility and carrier concentration. In real experi- ments, there is also the interaction between the applied pulse and electrostatic.…”

Metallic core conduction in unintentionally doped ZnO nanowire

“…Numerous papers reported the interaction mechanisms of ZnO wire surfaces with oxygen and hydrogen species. [1][2][3][4][5][6] When these species are adsorbed to the wire surface, charge transfer from the ZnO NW to the adsorbed species induces band bending that can appear as either an electron depletion layer or an electron accumulation layer. UV illumination or electron beam bombardment could break the bonds between the ZnO NW and the species 7,8) and could even create persistent conduction in ZnO wires.…”

Diameter-Dependent Surface Photovoltage and Surface State Density in Single Semiconductor Nanowires

“…22,23 Other surface adsorbates including hydrogen and hydroxyl groups can also play a role in surface state formation. 24 Among these, the oxygen-induced surface states have been shown to be the dominant species in ambient air in ZnO nanowires 25 and thus will be the focus of this study. These acceptor-type states, usually occupied by electrons as their energy levels are below the Fermi level in n-type ZnO under equilibrium, can capture photogenerated holes and thus play an important role in limiting hole transport.…”