Fermi level shifting of TiO2 nanostructures during dense electronic excitation

Abstract

Scanning Kelvin probe microscopy has been used to understand the modification of work function of TiO2 with swift heavy ion irradiation. The observed increase in contact potential difference (CPD) indicates a shift in Fermi level towards the valence band, which is due to the development of defects during the bombardment of high energy heavy ions. The change in CPD values on ion irradiation is attributed to electronic excitation induced defect concentration and surface roughness.

Evolution of damage fraction due to dense ionizing irradiation on TiO2 film

“…Similar type of SHI irradiation induced grain growth was also observed by other research groups [7,22]. The grains growth is expected due to generation of point defects and extended defects (oxygen vacancies) on the surface of TiO 2 due to electronic excitation [2,23]. With irradiation the defects concentration increases up to a dose of 5 × 10 12 ions cm −2 , beyond which it decreases with increasing fluence, due to annihilation of defects [7,24].…”

“…Titanium dioxide (TiO 2 ) is most widely used material because of its excellent optoelectronic properties [1][2][3][4][5]. Swift heavy ion (SHI) irradiation causes dense ionization and induces modification in its structural, morphological and electronic properties [6][7][8].…”

“…SHI beam induces point and extended defect on the surface of the film. The defects concentration increases with increasing ion fluence and affects the surface topography and surface potential of TiO 2 nanocrystalline thin film [2,7]. An estimation of radius of an equivalent cylinder confining disordered phase is done in terms of damage cross section.…”

“…The energy of the Ag ion beam is chosen to keep the range of the beam in the material larger than the film thickness, so that ion beam easily passes through the film. The morphological and local electronic properties of TiO 2 thin film modified SHI beam irradiation were analyzed using atomic force microscopy (AFM) and scanning Kelvin probe (SKP) microscopy respectively [2,12]. The grains growth and surface morphology on TiO 2 thin films are investigated by AFM followed by power spectral density (PSD) analysis [13].…”

Silver metalized mixed phase manganese-doped titania: Variation of electric field and band bending within the space charge region with respect to the silver content

“…Among the semiconductors employed, TiO 2 is most widely used because of its suitable flat band potential, chemical state, non-toxicity, strong oxidation capacity and also its high photocatalytic activity. However the use of TiO 2 is impaired by its wide band gap (∼3.2 eV), which requires UV light for photoactivation, and its major limitation is higher recombination rate of the photogenerated charge carriers resulting in lower quantum yield [2][3][4][5][6][7][8]. In this regard our research group had previously reported the incorporation of the paramagnetic Mn 2+ ions in anatase lattice at Ti 4+ substitution site [9].…”