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In this article, a field-induced electron emission from hydrogen (H)-terminated surface of heavily phosphorus (P)-doped diamond is discussed based on the barrier lowering model. Ultraviolet photoelectron spectroscopy suggested that an upward band bending of 1.45 eV existed at the surface of the diamond. A field emission characteristic as a function of the distance between an anode and diamond was measured to evaluate an average electric field in the vacuum. The barrier lowering model was introduced to estimate the reduction of the internal barrier due to the electric field at the diamond surface. The barrier lowering effect was confirmed from energies of emitted electrons, measured by combined ultraviolet photoelectron spectroscopy/field-induced electron spectroscopy (UPS/FES). As a result, it was shown that the electron emission from n-type diamond having NEA surface could be modulated by controlling a local electric field.

In this article, we introduce an electrochemical doping method of amorphous selenium (a-Se) using NaCl(aq). Recently, an a-Se photovoltaic device fabricated using this method [I. Saito, W. Miyazaki, M. Onishi, Y. Kudo, T. Masuzawa, T. Yamada, A. Koh, D. Chua, K. Soga, M. Overend, M. Aono, G. A. J. Amaratunga, and K. Okano, Appl. Phys. Lett. 98, 152102 (2011)] has been announced and opened up the potential of a new impurity doping method. This study will further explore its possibilities by doping chlorine (Cl) and sodium (Na) and aim to fabricate a p–n junction by reversing the applied voltage during the electrolysis. The device is characterized through photoelectric measurements. The I–V characteristics show rectification under light illumination.

Field emission from heavily phosphorus-doped homoepitaxial (111) diamonds after surface modifications are discussed. To develop a model for emission, we applied X-ray photoelectron spectroscopy (XPS) to characterize surface properties of H-plasma treated, oxidized and carbon-reconstructed surfaces. In addition, reflection high energy electron diffraction (RHEED) is used to evaluate atomic arrangements. Atomic force microscopy (AFM) is used to investigate surface morphologies. From AFM, no major difference is observed between H-terminated, oxidized and carbon reconstructed surfaces. Field emission properties of carbon reconstructed surfaces show a lower threshold than hydrogen-terminated or oxidized surfaces.

Heavily nitrogen (N)-doped polycrystalline diamond is reported to have excellent electron emission properties although its emission sites are limited. This report describes the fabrication processes, characterisation and electron emission properties of N-doped heteroepitaxial diamond which posses high potential as broad area emitter devices. We have obtained epitaxial diamond films on iridium (Ir) substrates by hot filament CVD using urea [(NH 2 ) 2 CO] as a dopant for N. The Ir substrates are bias treated via direct current plasma CVD (d.c. plasma CVD) method prior to the growth. Surface of the deposited films is smooth and continuous in scanning electron microscopy (SEM) observation. The epitaxial diamond growth is confirmed from reflective high energy electron diffraction (RHEED) pattern. It is found that the electron emission from heteroepitaxial diamond film is dominated by standard Fowler-Nordheim type emission due to the existence of strong electric field in the vacuum with the value of 26 V/μm.

It was reported that although nitrogen (N) forms either 1.7 or 4.0 eV deep level donor in diamond, these levels do not contribute to the electrical conduction at room temperature. It was also reported that hydrogen (H)-termination of diamond surfaces results in the p-type electrical conduction in CVD diamond, and that this conduction can be diminished by subsequent oxygen (O) treatment. In this paper, the conduction type of N-doped CVD diamond studied through thermoelectric measurements is presented. The measurements of the Seebeck coefficient indicate that: (i) as-grown N-doped CVD diamond shows p-type conduction, (ii) once it is oxidized, it presents n-type electrical conduction with carrier concentrations of about 10 1 8 cm - 3 . The results suggest the presence of competing bipolar transport between the surface and the bulk in CVD diamond.

In this study, photoconductor made of amorphous selenium (a-Se) is studied to improve a sensitivity of vacuum-tube type photodetectors. An electrochemical process was applied to a-Se films to form a p-n structure within the film. The formation of p-n structure was confirmed by time-of-flight secondary ion mass spectroscopy as well as its electronic property. The a-Se film was then combined into a prototype photodetector, and enhancement of sensitivity was evaluated in terms of nominal quantum efficiency and signal-to-noise ratio. The results showed that the formation of a p-n junction within a-Se film increased the sensitivity of the photodetector, especially at relatively low operation voltages.

sp 3 and sp 2 -rich nitrogen (N)-doped diamond electron emitters are prepared by modifying the substrate temperature. Their electron emission properties have been measured in order to examine the effect of the sp 2 /sp 3 ratio on the electron emission from N-doped diamond. The obtained electron emitters have been characterized by reflective high energy electron diffraction, X-ray diffraction and Raman spectroscopy. The electrical resistivities of the sp 3 -rich diamond is 100 G Ω cm or higher while that of the sp 2 -rich diamond is 100 Ω cm. In electron emission characteristics, the threshold voltage of the sp 3 -rich emitter is found to be lower than that of the sp 2 -rich emitter. From the threshold voltage versus the anode-diamond spacing characteristics, it has been found that most of the anode voltage drops in the bulk of the sp 3 -rich emitter and almost no voltage drop takes place in the sp 2 -rich emitter. The difference in electron emission properties should be explained by the resistivity of the N-doped diamond bulk.