The transport physics of domain wall conductivity in La-doped bismuth ferrite (BiFeO3) has been probed using variable temperature conducting atomic force microscopy and piezoresponse force microscopy in samples with arrays of domain walls in the as-grown state. Nanoscale current measurements are investigated as a function of bias and temperature and are shown to be consistent with distinct electronic properties at the domain walls leading to changes in the observed local conductivity. Our observation is well described within a band picture of the observed electronic conduction. Finally, we demonstrate an additional degree of control of the wall conductivity through chemical doping with oxygen vacancies, thus influencing the local conductive state.

In the present investigation, Kelvin probe force microscopy (KPFM) is used to study the charge separation, shift in Fermi level position and interfacial depletion region formation in a single cadmium sulfide (CdS)-copper sulfide (CuxS) nanorod heterojunction fabricated using hydrothermal synthesis and a topotaxial conversion reaction. A detailed analysis of KPFM images in the dark shows work function (or Fermi energy) values of CdS and CuxS regions consistent with the energy band diagram of the CdS-CuxS junction. Under illumination, Fermi energy levels of both the CuxS and CdS shift away from the vacuum level by 0.2 and 0.4 eV, respectively, which is very different from the behaviour expected in the case of a bulk p-n junction. The existence of interfacial regions topographically placed between ITO-CdS and CdS-CuxS with intermediate work function values as well as the observed narrowing of the work function spread under illumination are important for understanding the fundamental process of charge separation and junction formation in semiconductor nanorod solar cells.

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The influence of swift heavy (180 MeV 107Ag14+) ion irradiation on Au/n-Si Schottky diode characteristics has been analysed using in situ current–voltage (I–V) characterization. The values of the Schottky barrier height (SBH), the ideality factor and series resistance Rs for each irradiation fluence have been obtained from the forward bias I–V characteristics. For an unirradiated diode, the SBH and ideality factor were 0.74 ± 0.01 eV and 1.71, respectively. The barrier height decreases to 0.69 ± 0.01 eV as the fluence increases to a value of 1 × 1011 ions cm−2. It is found that after an irradiation fluence of 1 × 1011 ions cm−2 the SBH remains immune to further irradiation up to a fluence of 5 × 1012 ions cm−2. The observed behaviour is interpreted on the basis of energy loss mechanisms of energetic ions at the metal–semiconductor interface and irradiation-induced defects.

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