We propose an Au-free ohmic contact for diamond using a Ti/Al/Ti/TiN multi-layer metal stack, achieving an ultra-low specific ohmic contact resistance of 3.9 & times;10-5 Omega & centerdot;cm2. Building on this optimized contact structure, diamond Schottky barrier diodes (SBDs) are fabricated, exhibiting a breakdown voltage of 1770 V. This work provides a feasible and cost-effective route for the large-scale commercialization of diamond-based electronic devices.

Radiation detectors are important device-level characterization tools of the carrier dynamics of diamond as an ultrawide-bandgap semiconductor. Herein, a high-quality single-crystal diamond was grown on a high-temperature and high-pressure diamond substrate through microwave plasma chemical vapor deposition. We achieved the enhancement of microwave power density by compressing a plasma ball and optimizing the carbon-hydrogen ratio (C/H) within the plasma and thus considerably diminished the impurity and dislocation densities of the diamond epilayer. The full width at half maximum of the X-ray (004) reflection rocking curve was 15 arcsec, and no impurity emission bands were detectable in the photoluminescence spectrum at room temperature (25°C). The radiation detector made from this 200-µm-thick diamond epifilm demonstrated an α-particle response with a charge collection efficiency of 97.03

The 14-mm-large mosaic single crystal diamond (SCD) was prepared by splicing four diamond substrates with 7 mm side lengths by microwave plasma chemical vapor deposition (MPCVD). The characterization of the mosaic spliced SCD showed that even in the spliced interfaces without polycrystals or cracks, the stress, impurity, and defect density at the spliced interface were higher than those in nonspliced areas. Then, the hydrogen-terminated diamond (H-diamond)/metal–oxide semiconductor field-effect transistors (FETs) were prepared on this sample. The device characteristics were measured to study the influence of the splicing interface on device characteristics. The device made on the in-plain SCD exhibited the highest maximum saturation drain current density of $-$ 600.32 mA/mm and a minimum resistance of 15.2 $\Omega\cdot \text{mm}$ at a $\textit{V}_{\text{GS}}$ of $-$ 2 V; however, when the device was fabricated on the interface with significant cracks and polycrystals, the device characteristics had significant degradation. At the same time, when the splicing interface was free from polycrystals or cracks, although the device output current somehow decreased, the ON/OFF ratio and stability of the device were comparable with the device fabricated on the in-plain SCD region. We believe that the device performance can catch up with the device fabricated on the normal region in the future by optimizing the interface quality, and this kind of interface can be directly used to prepare devices.

Diamond silicon vacancy centers (SiV centers) have important application prospects in quantum information technology and biomarkers. In this work, the formation mechanism and regulation method of SiV center during the growth of polycrystalline diamond on silicon substrate are studied. By changing the ratio of nitrogen content to oxygen content in the growing atmosphere of diamond, the photoluminescence intensity of SiV center can be controlled effectively, and polycrystalline diamond samples with the ratios of SiV center photoluminescence peak to diamond intrinsic peak as high as 334.46 and as low as 1.48 are prepared. It is found that nitrogen promotes the formation of SiV center in the growth process, and the inhibition of oxygen. The surface morphology and photoluminescence spectrum for each of these samples show that the photoluminescence peak intensity of SiV center is positively correlated with the grain size of diamond, and the SiV center’s photoluminescence peak in the diamond film with obvious preferred orientation of crystal plane is higher. The distribution of Si centers and SiV centers on the surface of polycrystalline diamond are further characterized and analyzed by photoluminescence, Raman surface scanning and depth scanning spectroscopy. It is found that during the growth of polycrystalline diamond, the substrate silicon diffuses first into the diamond grain and then into the crystal structure to form the SiV center. This paper provides a theoretical basis for the development and application of SiV centers in diamond.

A hydrogen terminated diamond MOSFET with MoO3/Si3N4 doubly stacked gate dielectrics was fabricated on a single crystalline diamond sample. Compared to a device with single MoO3 layer gate dielectrics, the device performance was improved due to the improvement in the gate voltage, which benefited from the doubly stacked gate dielectric. The device with 4 mu m gate length shows a maximum output current of 118.67 mA/mm and an ultra-low resistance of 36.15 omega mm at the gate voltage of -5 V. In addition, the device shows a maximum transconductance of 35 mS/mm. These results indicate that the dielectric with high work function has high potential to achieve a high-performance diamond MOSFET.

The cascode structure was fabricated by combining the H-diamond normally-ON p-FET with the Si normally-OFF p-FET. The cascode shows normally- OFF characteristics with the threshold voltage of −0.8 V and the maximum transconductance of 344.6 mS/mm. The maximum saturation drain current and minimum ON-resistance are 34.2 mA/mm and $18.74 ~\Omega \cdot $ mm, respectively. In addition, the cascode structure can work as an inverter. The voltage transfer characteristics (VTCs) and dynamic switching characteristics at the frequency of 200 Hz of the diamond cascode inverter were demonstrated first. These results indicate that the diamond cascode is suitable to be used to achieve diamond normally- OFF device and can also be used to work as the inverter.

Diamond has a wide band gap, high carrier mobility, and high thermal conductivity, thereby possessing great potential applications in high power, and high temperature electronics devices, and also inhigh temperature logic circuit. In this work, we fabricate a hydrogen terminated diamond metal-oxide-semiconductor field effect transistor (MOSFET) by using the atomic layer deposition grown Al2O3 as a gate dielectric and passivation layer. The device has a gate length and width of 4 μm and 50 μm, respectively. The device delivers a maximum output current of about 113.4 mA/mm at VGS of –6 V and an ultra-high on/off ratio of 109. In addition, we fabricate three resistors, respectively, with an interelectrode distance of 20, 80 and 160 μm, corresponding to the resistance value of 16.7, 69.5 and 136.4 kΩ, respectively. The logic inverter is realized by combining the MOSFET with the load resistance, and the characteristics of the logic inverter are demonstrated successfully, which indicates that the diamond MOSFET has great potential applications in future logic circuits.

In this study, the low-temperature micro-photoluminescence (PL) technology was employed to investigate the transformation of nitrogen-vacancy (NV), silicon-vacancy (SiV) centers in diamond crystal. Results showed that the NV and SiV luminescence were controlled by electron irradiation followed by thermal annealing. Both centers vanished together with the emergence of neutral single vacancy (GR1 center) after 200 keV electron irradiation. Interstitial related defects and vacancies were activated to diffuse by annealing (above ∼400 and 700 °C, respectively). The vacancies migrated to be captured by N and Si atoms due to the strain fields around the atoms attracted vacancies, and the NV and SiV centers appeared again in the PL spectra. In addition, compared the annealing behavior with NV center, the new emission at 639.7 nm was attributed to the nitrogen combined with carbon interstitials.

In this work, we conduct a temperature-dependent study of optical centres in ultrapure diamond after 200 keV irradiation by photoluminescence spectra, which are performed in a temperature range of 80–200 K. The zero phonon lines (ZPLs) include sizes of 550.3 nm, 593 nm, and 741 nm (GR1 centre). With an increase in measurement temperature, the ZPLs shift to the lower energy side, together with intensity quenching and an increase in the full width at half maximum. These results are noted in models of lattice contraction and electron–phonon coupling, and their inhomogeneous and homogeneous broadening mechanisms are also carefully distinguished by the Voigt function. The 550.3 nm and 593 nm emissions present harder bonds than the GR1 centre, close thermal quenching energies to the interstitial-related defect, a lower thermal softness than that of the ideal diamond, weak phonon bands at each lower energy side, and different broadening mechanisms with the GR1 centre, indicating that the 550.3 nm and 593 nm lines are possibly interstitial-related.

硼是金刚石中最常见的受主元素之一,其在价带之上0.37 eV处形成了浅能级,因此硼掺杂金刚石被认为是一种理想的p型半导体材料.在化学气相沉积法制备的硼掺杂金刚石中,硼杂质在晶体中的分布非常不均匀,其拉曼信号强度对测试位置的依赖性非常强,且可重复性很差.而对于高温高压法合成的硼掺杂金刚石来说,同一晶面上硼杂质分布变化较小.本文利用低温光致发光光谱研究了高温高压法合成的硼掺杂金刚石辐照缺陷的光致发光性质,并利用晶体生长理论讨论了辐照缺陷在不同晶面上的分布情况.

Diamond is a wide bandgap semiconducting material, and electron irradiation is a good modification method for diamond. When the diamond with a thickness of 0.1 mm is irradiated with MeV electrons, the irradiation defects will be evenly distributed in the crystal. However, when the electron irradiation energy is 200 keV, the situation is different. The distribution of irradiation defects is not uniform, so these distributions cannot be ignored. In this work, the low-temperature photoluminescence method is employed to study the optical defects and their depth penetration in 200 keV electron irradiated IIa diamond. With the increase of depth penetration, the intensities of 2.091 eV emission and GR1 emission decrease accompanied by the enhancement of nitrogen vacancy (NV) intensity. The attenuation coefficients are 0.068 mu m(-1)for 2.091 eV emission and 0.045 mu m(-1)for GR1 emission, respectively. However, the enhancement coefficient is 0.02 mu m(-1)for the NV center, which is quite close to the difference of attenuation coefficient between 2.091 eV and GR1 emissions. The results indicated that the 2.091 eV emission is possibly related to self-interstitials and during the irradiation, the self-interstitials annihilate with the vacancies in the structure of nitrogen-vacancy defects. Furthermore, the 2.091 eV emission has a larger migration distance of about 65 mu m, which is greater than GR1 emission (50 mu m). This work also concludes that vacancy-related optical defects more accurately characterize the actual penetration of radiation damage in diamonds than interstitial-related optical defects.

In this study, low temperature micro‐photoluminescence technology is used to investigate the development and migration of intrinsic defects in Si‐doped diamond. The results demonstrate that NV and Si‐V luminescence are weakened due to the recombination of self‐interstitials created by electron irradiation in diamond. After annealing at high temperatures, interstitial‐related centers disappear and the vacancy migrate significant distances to isolated N and Si atoms for conversion into NV and Si‐V centers.

本文利用激光共聚焦显微拉曼光谱仪表征了高温高压法合成的氮掺杂金刚石,并分析了该晶体的光致发光特性.结果表明,金刚石晶体内部含氮量比晶体表面高,且由于氮原子尺寸较大,使得晶体内部应力较高,晶化程度弱化;另外,氮掺杂金刚石的光致发光主要以氮-空位(NV)复合缺陷为主;氮含量高的区域,NV缺陷发光增强,且NV-/NV0强度比也增强.这是因为氮作为施主原子,有利于负电荷缺陷即NV-中心的形成;同时氮含量升高,也会使得费米能级向NV-中心的基态靠近,这也造成了NV-/NV0强度比随氮含量增加而增强.