Boron nitride (BN) is a promising semiconductor with a wide band gap ( approximately 6 eV). Here, we report the synthesis of vertically aligned BN nanosheets (BNNSs) on silicon substrates by microwave plasma chemical vapor deposition from a gas mixture of BF(3)-N(2)-H(2). The size, shape, thickness, density, and alignment of the BNNSs were well-controlled by appropriately changing the growth conditions. With changing the gas flow rates of BF(3) and H(2) as well as their ratio, the BNNSs evolve from three-dimensional with branches to two-dimensional with smooth surface and their thickness changes from 20 to below 5 nm. The growth of the BNNSs rather than uniform granular films is attributed to the particular chemical properties of the gas system, mainly the strong etching effect of fluorine. The alignment of the BNNSs is possibly induced by the electrical field generated in plasma sheath. Strong UV light emission with a broad band ranging from 200 to 400 nm and superhydrophobicity with contact angles over 150 degrees were obtained for the vertically aligned BNNSs. The present BNNSs possess the properties complementary to carbon nanosheets such as intrinsically semiconducting, high temperature stability, and high chemical inertness and may find applications in ultraviolet nanoelectronics, catalyst supports, electron field emission, and self-cleaning coatings, etc., especially those working at high temperature and in harsh environments.

Cubic BN (cBN) has a set of extreme properties similar or even superior to diamond. The advance of science and technology of cBN has however been severely hampered by the poor quality of the material available (random orientation, limited film thickness, poor crystallinity and adhesion with substrates due to a non-cubic BN interlayer). This paper reviews the recent progress in the nucleation, growth and characterization techniques of cBN films. It describes various successful approaches in interface engineering and growth techniques in increasing film thickness, improving crystallinity and adhesion of cBN films to the substrate, which are the major issues hindering cBN films for both mechanical and electronic applications. Based on observations of the surface and interface structures, we further discuss the growth mechanisms of cBN films via physical and chemical routes.

Deep-ultraviolet (DUV) solar-blind photodetectors based on high-quality cubic boron nitride (cBN) films with a metal/semiconductor/metal configuration were fabricated. The design of interdigitated circular electrodes enables high homogeneity of electric field between pads. The DUV photodetectors present a peak responsivity at 180nm with a very sharp cutoff wavelength at 193nm and a visible rejection ratio (180 versus 250nm) of more than four orders of magnitude. The characteristics of the photodetectors present extremely low dark current, high breakdown voltage, and high responsivity, suggesting that cBN films are very promising for DUV sensing.

High-density, uniform diamond nanopillar arrays were fabricated by employing bias-assisted reactive ion etching in a hydrogen/argon plasma. Gold nanodots were employed as etching masks. The formation of nanopillar structure is associated with the directional physical etching/sputtering by ion bombardment and selective chemical etching of sp2 carbons by reactive hydrogen atoms and ions. The density and geometry of the nanopillars depend on the initial structure of diamond films and reactive ion etching conditions. The nanopillars with high aspect ratio and large surface area may have potential applications in high-efficiency and high-sensitivity diamond-based biomedical and chemical sensors and in mechanical and thermal management.

Future missions for space astronomy and solar research require innovative vacuum ultraviolet (VUV) photodetectors. Present UV and VUV detectors exhibit serious limitations in performance, technology complexity and lifetime stability. New developments of metal-semiconductor-metal (MSM) solar-blind photodetectors based on diamond, cubic boron nitride (c-BN), and wurtzite aluminium nitride (AlN) are reported. In the wavelength range of interest, the characteristics of the MSM photodetectors present extremely low dark current, high breakdown voltage, and good responsivity. Diamond, c-BN, and AlN MSM photodetectors are sensitive and stable under UV irradiation. They show a 200 nm to 400 nm rejection ratio of more than four orders of magnitude and demonstrate the advantages of wide band gap materials for VUV radiation detection in space.