The properties of ultraviolet (UV) photodetector fabricated on TiO₂/diamond film were investigated. Single crystal diamond layer was grown on high-pressure-high-temperature Ib-type diamond substrate by microwave plasma chemical vapor deposition method, upon which TiO₂ film was prepared directly using radio frequency magnetron sputtering technique in Ar and O₂ mixing atmosphere. Tungsten was used as electrode material to fabricate metal-semiconductor-metal UV photodetector. The dark current is measured to be 1.12 pA at 30 V. The photo response of the device displays an obvious selectivity between UV and visible light and the UV-to-visible rejection ratio can reach 2 orders of magnitude. Compared with that directly on diamond film, photodetector on TiO₂/diamond film shows higher responsivity.

In this study, a NiO/diamond UV-photodetector has been fabricated and investigated. A single crystal diamond (SCD) layer was grown on a high-pressure-high-temperature Ib-type diamond substrate by using a microwave plasma chemical vapor deposition system. NiO films were deposited directly by the reactive magnetron sputtering technique in a mixture gas of oxygen and argon onto the SCD layer. Gold films were patterned on NiO films as electrodes to form the metal-semiconductor-metal UV-photodetector which shows good repeatability and a 2 orders of magnitude UV/visible rejection ratio. Also, the NiO/diamond photodetector has a higher responsivity and a wider response range in contrast to a diamond photodetector.

A normally off hydrogen-terminated diamond (H-terminated diamond) field-effect transistor (FET) has been successfully achieved with Ti/TiOₓ gate materials. A 5-nm Ti film was deposited on H-terminated diamond by electron beam evaporation technique and then it was thermally oxidized in air at 120 °C for 10 h to form Ti/TiOₓ, which was confirmed by X-ray photoelectron spectroscopy. The threshold voltage of H-terminated diamond FET is -0.14 V at VDS of -8 V, indicating a normally off operation. The normally off property could be attributed to the difference of work difference between Ti and H-terminated diamond, which may deplete the hole carriers in H-terminated diamond 2-D hole gas (2DHG) conduction channel. The maximum mobility of H-terminated diamond FET is 313 cm²/Vs at VGS of -0.2 V. And, the fixed negative charge density is 3.37 x 10₁₁ cm⁻². The results demonstrate that Ti/TiOₓ H-terminated diamond FET is a good solution to fabricate normally off device with a simple fabrication process, undamaged 2DHG channel, and uncontaminated interface between Ti and TiOₓ gate materials, which may promote the development of normally off H-terminated diamond FET.

Three dimensional diamond ultraviolet (UV) photodetector have been fabricated on diamond epitaxial layer through down-top approach, where diamond epitaxial layer was grown between metal electrodes. A thin diamond epitaxial layer was first grown on high-pressure high-temperature single crystal diamond substrate. Then, the diamond epitaxial layer was covered by interdigitated tungsten electrodes. Furthermore, another diamond epitaxial layer was grown on uncovered area. At last, UV-Ozone treatment was used to oxidize the surface. The optoelectronic performance of the photodetector was characterized, exhibiting a large responsivity and a repeatable transient response behavior. Moreover, down-top process is beneficial for the electrode conductivity stability. Also, an ohmic contact could be formed between tungsten and diamond during growth. The results indicate that down-top process is an efficient way for fabrication of three dimensional diamond photodetectors.

Conventional periodic structures usually have nontunable refractive indices and thus lead to immutable photonic bandgaps. A periodic structure created in an ultracold atoms ensemble by externally controlled light can overcome this disadvantage and enable lots of promising applications. Here, two novel types of optically induced square lattices, i.e., the amplitude and phase lattices, are proposed in an ultracold atoms ensemble by interfering four ordinary plane waves under different parameter conditions. We demonstrate that in the far-field regime, the atomic amplitude lattice with high transmissivity behaves similarly to an ideal pure sinusoidal amplitude lattice, whereas the atomic phase lattices capable of producing phase excursion across a weak probe beam along with high transmissivity remains equally ideal. Moreover, we identify that the quality of Talbot imaging about a phase lattice is greatly improved when compared with an amplitude lattice. Such an atomic lattice could find applications in all-optical switching at the few photons level and paves the way for imaging ultracold atoms or molecules both in the near-field and in the far-field with a nondestructive and lensless approach.

Fabrication of single crystal hydrogen-terminated diamond MOSFET with dielectrics of LiF/Al2O3 has been successfully carried out. After patterning source and drain electrodes, 60nm LiF/ 20nm Al2O3 were deposited as dielectrics. The output and transfer characteristics were investigated, indicating the typical p-type channel MOSFET. The on/off ratio was ~109, which was high enough for practical applications. The fixed and trapped charge in LiF/Al2O3 were also examined. Based on the capacitance-voltage curves, the dielectric constant of LiF/Al2O3 was calculated to be 36.1, which was ascribed to the LiF supercapacitor structure. To the best of our knowledge, this LiF supercapacitor structure was first used in hydrogen-terminated diamond MOSFET to improve the dielectric constant.