Shaoheng Cheng

Fabrication and characteristics of nitrogen-doped nanocrystalline diamond/p-type silicon heterojunction

Nitrogen-doped nanocrystalline diamond films (N-NDFs) have been deposited on p-type silicon (Si) by microwave plasma chemical vapor deposition. The reaction gases are methane, hydrogen, and nitrogen without the conventional argon (Ar). The N-NDFs were characterized by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The grain sizes are of 8∼10 nm in dimension. The N-NDF shows n-type behavior and the corresponding N-NDF/p-Si heterojunction diodes are realized with a high rectification ratio of 102 at ∼ 7.8 V, and the current density reaches to 1.35 A/cm2 at forward voltage of 8.5 V. The findings suggest that fabricated by CH4/H2/N2 without Ar, the N-NDFs and the related rectifying diodes are favorable for achieving high performance diamond-based optoelectronic devices.

Ultraviolet photoelectrical properties of a n-ZnO nanorods/p-diamond heterojunction

The ultraviolet (UV) photoresponse properties of a n-ZnO nanorods/p-diamond heterojunction were investigated by studying the dark and photo I–V characteristics. It shows typical rectifying behavior with a rectification ratio of 3.2 and 8.8 at 5 V for the dark current and the photocurrent, respectively. The turn on voltage under UV illumination is three times lower than that under the dark current and the ideality factor of the device is decreased. The forward current under UV illumination is more than 4 times higher than the dark one at 10 V whereas the leakage current shows a little increase at −10 V. The electrical transport behaviors are investigated both under the dark current and the photocurrent. The photogenerated charges and their transfer processes were analyzed by surface photovoltage (SPV) measurements.

Effect of nitrogen on deposition and field emission properties of boron-doped micro- and nano-crystalline diamond films

In this paper, we report the effect of nitrogen on the deposition and properties of boron doped diamond films synthesized by hot filament chemical vapor deposition. The diamond films consisting of micro-grains (nano-grains) were realized with low (high) boron source flow rate during the growth processes. The transition of micro-grains to nano-grains is speculated to be strongly (weekly) related with the boron (nitrogen) flow rate. The grain size and Raman spectral feature vary insignificantly as a function of the nitrogen introduction at a certain boron flow rate. The variation of electron field emission characteristics dependent on nitrogen is different between microcrystalline and nanocrystalline boron doped diamond samples, which are related to the combined phase composition, boron doping level and texture structure. There is an optimum nitrogen proportion to improve the field emission properties of the boron-doped films.

Fabrication, characterization and optical properties of TiO2 nanotube arrays on boron-doped diamond film through liquid phase deposition

TiO2 nanotube(TiNT) arrays were deposited on boron-doped diamond films by a liquid-phase deposition method with ZnO nanorod arrays as the template. The different morphologies of TiNTs have been obtained by controlling the morphology of ZnO template. The X-ray diffraction and energy-dispersive X-ray analysis show that the ZnO nanorod arrays template has been removed in the TiNTs formation process. The crystalline quality of the TiNTs is improved by increasing the annealing temperature. The band gap of the TiNTs is about 3.25 eV estimated by the UV-Vis absorption spectroscopy, which is close to the value of bulk TiO2. In the photoluminescence spectrum, a broad visible emission in a range of ca. 550–750 nm appears due to the surface oxygen vacancies and defects.

Plasmon resonance enhanced temperature-dependent photoluminescence of Si-V centers in diamond

Temperature dependent optical property of diamond has been considered as a very important factor for realizing high performance diamond-based optoelectronic devices. The photoluminescence feature of the zero phonon line of silicon-vacancy (Si-V) centers in Si-doped chemical vapor deposited single crystal diamond (SCD) with localized surface plasmon resonance (LSPR) induced by gold nanoparticles has been studied at temperatures ranging from liquid nitrogen temperature to 473 K, as compared with that of the SCD counterpart in absence of the LSPR. It is found that with LSPR the emission intensities of Si-V centers are significantly enhanced by factors of tens and the magnitudes of the redshift (width) of the emissions become smaller (narrower), in comparison with those of normal emissions without plasmon resonance. More interestingly, these strong Si-V emissions appear remarkably at temperatures up to 473 K, while the spectral feature was not reported in previous studies on the intrinsic Si-doped diamonds wh...

Fabrication of a hybrid structure of diamond nanopits infilled with a gold nanoparticle

A hybrid structure of a gold-nanoparticle (Au-NP)/diamond-nanopit has been fabricated by using a simple procedure of oxygen plasma etching of a Au-coated single crystal diamond. The nanopit is of an inversely truncated pyramidal shaped, and is filled with a Au NP located at the bottom. The formation process is thoroughly investigated. It was found that the structure was induced by the interaction of oxygen plasma etching and the plasma enhancement effect of Au NP. Here, the Au NPs enhanced the etching process, which is completely different from the masking effect in the formation of diamond nanowires/rods. In addition, after the Au NPs were removed by soaking in aqua regia, the structure served as a structural template for fabricating pyramid-structured poly(dimethylsiloxane) sheets.

Fabrication and high temperature electronic behaviors of n-WO3 nanorods/p-diamond heterojunction

This work explores the temperature-dependent characteristic and carrier transport behavior of a heterojunction of n-WO3 nanorods (NRs)/p-diamond. The n-type WO3 NRs grown by the hydrothermal method were deposited on a p-type boron-doped diamond film. The p-n heterojunction devices showed good thermal stability and have rectification characteristic from room temperature up to 290 °C. With increasing temperature, the turn-on voltages were decreased, and the rectification ratios were relatively high. The calculated ideality factor of the device decreased monotonously with increased temperature. The carrier transport mechanisms at different applied bias voltages following Ohmic laws, recombination-tunneling, and space-charge-limited current conduction of the heterojunction are discussed depending on temperature.

A review on the low-dimensional and hybridized nanostructured diamond films

In the last decade, besides the breakthrough of high-rate growth of chemical vapor deposited single-crystal diamonds, numerous nanostructured diamond films have been rapidly developed in the research fields of the diamond-based sciences and industrial applications. The low-dimensional diamonds of two-dimensional atomic-thick nanofilms and nanostructural diamond on the surface of bulk diamond films have been theoretically and experimentally investigated. In addition, the diamond-related hybrid nanostructures of n-type oxide/p-type diamond and n-type nitride/p-type diamond, having high performance physical and chemical properties, are proposed for further applications. In this review, we first briefly introduce the three categories of diamond nanostructures and then outline the current advances in these topics, including their design, fabrication, characterization, and properties. Finally, we address the remaining challenges in the research field and the future activities.

Boron-Doped Diamond-Film-Based Two-Dimensional Electrode of Electrophoresis Tank*

Chemically robust conductive p-type boron-doped diamond (BDD) films are an important electrode material and have been widely applied in electrochemistry. In this study, BDD films are taken as a two-dimensional (2D) electrode in a electrophoresis tank system instead of the conventional one-dimensional platinum wire electrode. The theoretical simulations by finite element numerical analysis reveal that the 2D BDD electrodes have relatively high intensity and uniformity of electric field in the tank. Experimentally, the 2D BDD electrodes with smaller size show excellent properties for the separation of DNA fragments. The advantages of the 2D BDD electrodes with chemical inertness, sustainability, high intensity and uniformity electronic field, as well as reduced small size of electrophoresis tank would open a possibility for realizing new generation, high-performance biological devices.