High temperature photoelectron emission and surface photovoltage in semiconducting diamond

Abstract

Sponsorship: EPSRC RONO: EP/G068216/1A non-equilibrium photovoltage is generated in semiconducting diamond at above-ambient temperatures during x-ray and UV illumination that is sensitive to surface conductivity. The H-termination of a moderately doped p-type diamond (111) surface sustains a surface photovoltage up to 700K, while the clean (21) reconstructed surface is not as severely affected. The flat-band C 1s binding energy is determined from 300K measurement to be 283.87 eV. The true value for the H-terminated surface, determined from high temperature measurement, is (285.260.1) eV, corresponding to a valence band maximum lying 1.6 eV below the Fermi level. This is similar to that of the reconstructed (21) surface, although this surface shows a wider spread of binding energy between 285.2 and 285.4 eV. Photovoltage quantification and correction are enabled by real-time photoelectron spectroscopy applied during annealing cycles between 300K and 1200K. A model is presented that accounts for the measured surface photovoltage in terms of a temperature-dependent resistance. A large, high temperature photovoltage that is sensitive to surface conductivity and photon flux suggests a new way to use moderately B-doped diamond in voltage-based sensing devicespublishersversionPeer reviewe

Identifying chemical and physical changes in wide-gap semiconductors using real-time and near ambient-pressure XPS

“…4a) was found to have an apparent binding energy similar to graphite rather than its true value of 285.4 eV that is only revealed at the higher temperature. 38,39 This surface photovoltage was also observed for this diamond when irradiated with He I and synchrotron radiation at room temperature and was found to persist when measured at near-ambient pressure of oxygen. Ultraviolet Photoelectron Spectroscopy (UPS) measurements for this moderately-B-doped diamond at the higher temperature yield a barrier height that is close to that predicted by the charge neutrality level but is dependent on the surface preparation.…”

“…This reversible change is sensitive to the X-ray flux and is interpreted as a room temperature photovoltage, as reported for a H-terminated diamond (111) crystal with a similar boron concentration measured in the same environment. 38 For the (111) diamond, the observed shift and its saturation at higher temperature was modelled using the diamond resistivity as the main temperature-dependent variable. At room temperature, the photoexcitation process generates electrons and holes in the depletion region that are separated, with electrons accumulating at the surface when the resistance to earth in the diamond is high.…”

Origins of Diamond Surface Noise Probed by Correlating Single-Spin Measurements with Surface Spectroscopy

“…The electron analyzer was operated in wide angle mode to sample band edge states averaged in momentum space. Since the apparent binding energy of electron states measured by photoelectron spectroscopy is affected by surface charging and photovoltage generation 38 , we calibrate the valence band edge against the Fermi edge of a tantalum standard. Rear-view VG LEED optics were used to record surface electron diffraction patterns.…”

The occupied electronic structure of ultrathin boron doped diamond

“…An absolute energy calibration has been performed at hn ¼ 520 eV by integrating the photoemission background (away from any strong features) and identifying the Fermi level. This atypical second step is necessary to compensate for the possibility of a Schottky barrier between the sample and calibration foil, 38 as well as the possibility of a photovoltage generated by synchrotron light exposure, 39,40 both of which will manifest as an offset in the energy scale of the dataset.…”