Growth of nano-crystalline diamond on single-crystalline diamond by CVD method

Nanocrystalline (NC) diamond films are grown by chemical vapor deposition on various single crystal diamond faces. Under conditions of NC diamond growth, the growing filmmorphology is reduced to two planes: {100} and {111}. The {100} planes are smooth and homoepitaxial layerby-layer growth occurs on them, whereas the NC film formed by twin crystalliteswith sizes of several tens and hundreds nanometers grows on {111} planes. Nitrogen impurity sharply increases the diamond growth rate.     

Demonstration of diamond field effect transistors by AlN/diamond heterostructure

This is the first report on an AlN/diamond heterojunction field effect transistor (HFET). The AlN epilayer is grown on oxygen‐terminated (111) diamond substrates using metalorganic vapor phase epitaxy at a temperature as high as 1240 °C. The transistor and gate capacitance–voltage characteristics indicate that the HFET behaves as a p‐channel FET with a normally‐on depletion mode. The HFET channel is located at the AlN/diamond interface, and holes are accumulated in diamond close to the interface. The development of the AlN/diamond HFET creates a new possibility for diamond‐based power electronics. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Heterogeneous nucleation of diamond

We present theoretical study of the formation of diamond clusters on the non-diamond substrate. This phenomenon is modelled at the kinetic level and described by the Fokker-Planck-like equation governing the evolution of the distribution of newly-forming clusters. Incubation time of this process is calculated and compared with the experimental data.     

The physics of diamond

The accurate measurement of the thermal conductivity of metals still poses considerable experimental difficulty. The reasons for this, and the main ways in which the problem has been approached, are summarized. A detailed examination of the development in technique and methods of measurement shows that while most of the steady-state methods introduced over 50 years ago are still being improved, the emphasis in the last few years has been on the development of methods which give more rapid results, particularly at high temperatures.     

Data-driven exploration for pressure-induced superconductors using diamond anvil cell with boron-doped diamond electrodes and undoped diamond insulating layer

ABSTRACT

Data-driven exploration for pressure-induced superconductors was performed based on the high-throughput first-principles screening of electronic band structures. In the screening conditions, we focused on the characteristics including a narrow band gap, flat band feature, and possibility of metallization under high pressure. The 27 promising compounds were screened out from the database of Atomwork for the candidates of new pressure-induced superconductors. Among the candidates, we actually synthesized three compounds in a single crystal, and all candidates exhibited the pressure-induced superconductivity. For the in-situ electrical transport measurements, we developed a novel configuration of diamond anvil cell with boron-doped diamond electrodes and an undoped diamond insulating layer. The discovered new pressure-induced superconductors via the data-driven approach and the developed diamond anvil cell were summarized in this paper.     

Chemical vapor deposition of diamond

In the recent decade a multitude of diamond thin film production methods has been developed, generally based on chemical vapor deposition processes from thermally or plasma activated gas phases. Diagnostic studies, growth experiments and numerical kinetic investigations have in recent years lead to an improved understanding of the prerequisites of continuous diamond growth and of the chemical processes involved. While the mechanism of carbon incorporation into the diamond surface is not yet known completely, the gas-phase species which are essential in a diamond-growth atmosphere can be narrowed to a small number, whose role in the gas-phase chemistry is quite well known.     

Analysis of ion implanted diamond

Ion implantation allows controlled introduction of impurities into diamond. A basic problem is to determine if the implanted layers are dominated by substitutional doping or radiation damage effects. Optical and electrical measurements on the implanted diamonds revealed (1) a degradation of the band-gap and sample coloration, (2) no optical absorption levels which would be characteristic of hydrogenic ionization levels, (3) resistivity activation energies of 0.2 to 0.3 eV independent of the ion specie, and (4) no measurable Hall Effect.

Phosphorous implanted layers in diamond were analyzed by means of the channeling technique. It was shown that (1) the diamond retained the implanted phosphorous atoms during a vacuum anneal at 950°C which restored crystalline order, (2) the implanted phosphorous atoms did not assume either substitutional or tetrahedral interstitial sites, (3) the measured projected range for 70 keV phosphorous in diamond of 450 ± 115 Å was consistent with theoretical range calculations and (4) a stable monolayer of oxygen atoms (5.5 × 10¹⁵/cm²) exists on the {111} surface of implanted and annealed diamond. The results of the crystal analysis show that these electrical and optical properties are dominated by radiation damage and not substitutional doping mechanisms.     

金刚石薄膜电致发光研究

报道了金刚石薄膜电致发光现象.为进一步提高金刚石薄膜蓝区电致发光强度,分别采用了硼氮双掺杂法和稀土掺杂法制备出了金刚石薄膜电致发光器件,并采用低电容率的本征金刚石薄膜和氧化硅薄膜为绝缘层的夹层式器件结构.研究结果显示:采用稀土铈掺杂可以有效地提高金刚石薄膜蓝区电致发光强度,其蓝区最大电致发光强度可达3.5 cd/m2;采用低电容率绝缘膜的夹层式结构,能有效地提高电子进入发光层时的能量,并有助于提高器件发光的稳定性和发光寿命.     

Laser polishing of diamond plates

Results are reported on laser polishing of 150–400-μm-thick free-standing diamond films with either a copper vapor laser (510 nm wavelength) or an ArF excimer laser (193 nm wavelength). Studies were focused on three particular goals. First, we aimed at a choice of optimum conditions for laser polishing of thick diamond films. It was shown that the laser polishing conditions and the resulting surface roughness were controlled by varying the angle of incidence of a scanning laser beam and by polishing time. Second, the laser ablation technique was applied to remove a defective layer from the “substrate” side of the diamond plates in order to reduce optical losses due to absorption in this layer. Third, the structure of the laser-graphitized diamond surface was studied using UV, visible, and IR optical spectroscopy techniques in the course of the “step-by-step” oxidative removal of the graphitic layer with increasing temperature of the oxidation in ambient air. Once the graphitic layer was removed, the optical transmission in the UV-visible-IR spectral range of the diamond films polished under optimum conditions was measured and compared with the optical transmission of the mechanically polished diamond films. It was shown that the optical quality (in the long-wave infrared region) of the laser-polished diamond plates was sufficient to reach the transmittance value very close to the theoretical limit. Received: 20 October 1998 / Accepted: 8 March 1999 / Published online: 5 May 1999     

Low-energy electrodynamics of superconducting diamond

Heavily boron-doped, diamond films can become superconducting with critical temperatures Tc well above 4 K. Here we first measure the reflectivity of such a film down to 5 cm(-1), by also using coherent synchrotron radiation. We thus determine the optical gap 2Delta, the field penetration depth lambda, the range of action of the Ferrell-Glover-Tinkham sum rule, and the electron-phonon spectral function alpha2F(omega). We conclude that diamond behaves as a dirty BCS superconductor.     

Ground-state properties of boron-doped diamond

Boron-doped diamond undergoes an insulator-metal or even a superconducting transition at some critical value of the dopant concentration. We study the equilibrium lattice parameter and bulk modulus of boron-doped diamond experimentally and in the framework of the density functional method for different levels of boron doping. We theoretically consider the possibility for the boron atoms to occupy both substitutional and interstitial positions and investigate their influence on the electronic structure of the material. The data suggest that boron softens the lattice, but softening due to substitutions of carbon with boron is much weaker than due to incorporation of boron into interstitial positions. Theoretical results obtained for substitution of carbon are in very good agreement with our experiment. We present a concentration dependence of the lattice parameter in boron-doped diamond, which can be used for to identify the levels of boron doping in future experiments. The text was submitted by the authors in English.     

Deposition of thin diamond films

This short review summarizes basic knowledge about the diamond film growth. Fundamental technologies of diamond film fabrication are compared. Some factors affecting the diamond crystal growth are discussed.Support of this work by the Ångström Interdisciplinary Association for Thin Film Processing at Uppsala University is gratefully acknowledged.     

Photoluminescence spectra of ultradisperse diamond

The first study of materials based on ultradisperse diamond produced by detonation is reported. A luminescence band in the visible has been observed, and some of its structural features have been interpreted by analogy with the known luminescence bands of centers in synthetic and natural diamonds. A comparison of the spectra obtained from ultradisperse diamond samples with the surface modified by different chemical treatments suggests that their pattern is governed to a considerable extent by the presence of a graphitic layer on the grain surface. Fiz. Tverd. Tela (St. Petersburg) 39, 2156–2158 (December 1997)