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A review of diamond-metal contacts is presented with reference to reported values of interfacial potential (Schottky) barriers and their dependence on macroscopic and microscopic properties of the diamond surface, the interface and the metal. No simple model can account for the overall spread of p-diamond barriers, although there are, for certain metals, correlations with metal electronegativity, interface chemistry and diamond surface preparation. Detailed studies are presented for a selected contact (Al-p-diamond) using real-time monitoring during metal growth from sub-nanometre to bulk films and subsequent in situ heating to 1000 °C. This contact, prepared in a clean vacuum environment on characterized single-crystal substrates, provides a case study for a combined in situ electrical and spectroscopic investigation using IV measurements for macroscopic diodes and real-time photoelectron spectroscopy for nanoscale metal films. Band bending during growth leads to a rectifying contact with a measured IV barrier height of 1.05 V and an ideality factor of 1.4. A transition from layered to clustered growth of the metal film is revealed in the real-time measurements and this is confirmed by AFM. For the annealed contact, a direct correlation is revealed by real-time photoemission between the onset of interfacial carbide formation and the change from a rectifying to an ohmic contact at 482 °C.

Evans D A, Roberts O R, Vearey-Roberts A R, Langstaff D P, Twitchen D J and Schwitters M 2007 Direct observation of Schottky to ohmic transition in Al-diamond contacts using realtime photoelectron spectroscopy Appl. Phys. Lett. 91 132114 doi:10.1063/1.2790779Real-time photoelectron spectroscopy and in situ electrical measurements have been applied to the formation of Al contacts on p-type diamond. At 294 K, an initially uniform Al film induces band bending in the diamond consistent with the measured (current-voltage) barrier height of 1.05 V. The temperature-induced transition to an Ohmic contact has been monitored in real time revealing a direct correlation between the onset of surface bonding at 755 K and an abrupt change in surface band bending. The reaction temperature is lower than previously believed, and there is a second transition point at 1020 K where the rates of change of both reaction and band bending increase sharply.authorsversionPeer reviewe

Post-deposition molecular rearrangement in thin organic films is revealed by in situ real-time photoelectron spectroscopy during organic molecular beam deposition. Agreement between real time spectroscopy and Monte Carlo modeling confirms the role of nearest-neighbor molecular attraction in driving a time-dependent morphology for oriented films of tin phthalocyanine (SnPc) on a range of substrates. The time-dependent molecular self-organization occurs over timescales comparable to the growth rates and is therefore an important factor in the degradation of thin films of organic semiconductors typically considered for the fabrication of multilayer semiconductor devices. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775762]publishersversionPeer reviewe

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