We present the methodology used to fabricate an X-ray reflection grating and describe a technique for grating replication. Further, we present the experimental procedure and results of a study to measure the diffraction efficiency of a replicated X-ray reflection grating in an extreme off-plane geometry. The blazed grating demonstrates a total diffraction efficiency of similar to 60% from 0.34 to 1.2 keV at a grazing angle of similar to 1 degrees.5, with single-order efficiency ranging from similar to 35% to 65% for energies within the blaze envelope. The diffraction efficiency of the grating measured relative to the reflectivity of the metal coating averages similar to 90% above 0.34 keV. Data collected as a function of beam position on the grating indicate a relative variation in total efficiency of <1% rms across the grating surface.

Cathode hysteresis in the reactive pulsed dc sputtering of a vanadium metal target was investigated to correlate the structural and electrical properties of the resultant vanadium oxide thin films within the framework of Berg’s model [Berg et al., J. Vac. Sci. Technol. A 5, 202 (1987)]. The process hysteresis during reactive pulsed dc sputtering of a vanadium metal target was monitored by measuring the cathode (target) current under different total gas flow rates and oxygen-to-argon ratios for a power density of ∼6.6.W/cm2. Approximately 20%–25% hysteretic change in the cathode current was noticed between the metallic and oxidized states of the V-metal target. The extent of the hysteresis varied with changes in the mass flow of oxygen as predicted by Berg’s model. The corresponding microstructure of the films changed from columnar to equiaxed grain structure with increased oxygen flow rates. Micro-Raman spectroscopy indicates subtle changes in the film structure as a function of processing conditions. The resistivity, temperature coefficient of resistance, and charge transport mechanism, obeying the Meyer–Neldel relation [Meyer and Neldel, Z. Tech. Phys. (Leipzig) 12, 588 (1937)], were correlated with the cathode current hysteric behavior.

This paper reports a new phenomenon—decrystallization of a solid by 1–5 eV photons, in a few seconds. A polycrystalline, 20 μm thick layer of CVD diamond on a WC substrate was exposed to two simultaneous pulsed laser beams 308 nm excimer, and 1.06 μm Nd:YAG in air ambient. The rough surface was ablated and smoothed, but the upper exposed half of the diamond layer was shown by Raman spectroscopy and X-ray diffraction to have been transformed to a non-crystalline phase. The 1332 cm−1 Raman peak disappeared, demonstrating that lattice periodicity had been destroyed. Interestingly, the atomic disorder was gradually relaxed during five years at room temperature, and the Raman signature reappeared. The effect of decreasing intensity of diamond Raman peak has been demonstrated in single-crystal diamond. The distorted diamond lattice relaxed upon annealing in hydrogen plasma. The combination of pressure waves and the heating and cooling cycles is responsible for the creation and subsequent freezing of the atomic disorder, all in the solid state. The metastable states are introduced when atoms in the perfect lattice become displaced from the equilibrium positions. This is the process we term decrystallization—to distinguish it from glass formation, which requires the intermediary liquid state.

Highly doped n-type silicon powder responds aggressively to a 2.45-GHz microwave E-field, whereas it remains unperturbed in the H-field. In the E-field, after about 30 s of treatment, the silicon powder attained submelting temperatures and thus coagulated to a bulk solid piece. X-ray diffraction analysis of the surface and the cross section of this solid material failed to show any detectable peaks, ascertaining the fact that the material had decrystallized. The Raman spectra of the material had broad and shallow peaks quite different from the thin, sharp lines exhibited by Si wafer. It appears that the E-field treatment has considerably distorted the lattice structure creating lattice strains throughout the sample. These lattice strains were relieved by grinding (recrystallized).

Ternary B–C–N amorphous and crystalline coatings were deposited by microwave chemical vapor deposition using a mixture of NH3, CH4, B2H6 and H2 gases at substrate temperatures in the range 800–1350°C, and a gas pressure in the range (9.0–12)×103 Pa. We studied the influence of deposition conditions (i.e. gas composition, substrate temperature and material) on the coating structure, chemical composition and surface morphology. Both amorphous and polycrystalline coatings were deposited. Amorphous coatings were usually formed at lower substrate temperatures and were non-homogeneous across the coating thickness. Nanocrystalline inclusions of boron carbide, boron nitride and diamond were observed in amorphous B–C–N compounds. Polycrystalline coatings were generally represented by both diamond and boron nitride phases. In one case, a polycrystalline coating with the composition of B2CN4 was fabricated. The experimental results are discussed in detail.

Electron field emission measurements have been performed on thin film cold cathode materials grown, on molybdenum, by a modified MPACVD diamond process. Specifically the modification is due to the addition of nitrogen and oxygen, in varying ratios, during the diamond growth phase. Characterization using Raman spectroscopy shows features at 1190, 1330 and 1550 cm −1 . A simple triode device was fabricated for electron emission characterization. KAPTON® film is used as the insulating layer and a Mo mesh is used as the extraction gate electrode. The collector is an indium tin oxide (ITO) coated glass plate which is positively biased with respect to the gate electrode. Field emission characteristics have shown current measurements of greater than I microamp for fields of 40 V/micron. Gate currents are typically 1000 times greater than the emitted current. Issues currently being addressed include improvement in the total emitted current, current stability and device failure. We also present field emission measurements on diamond films grown by HFCVD.

Thin-film cold cathodes have been grown on molybdenum by a modified microwave assisted plasma chemical vapor deposition diamond process. Electron field-emission tests have been performed on the devices. The modification from the chemical vapor deposition diamond process includes the addition of N2 and O2 into the plasma during the growth stage. Characterization of these films indicates a disordered tetrahedral carbon structure. Raman spectroscopy shows a disturbance in the cubic symmetry of the lattice and x-ray diffraction indicates a disordered tetrahedral structure. Electron emission testing indicate low turn-on voltages. Current densities from 1 to 8 mA/cm2 can be obtained for applied fields of 5–8 V/μm. The results are explained in terms of a change in the electronic band structure and the formation of states in the band gap.

A new diamond deposition process utilizing a plasma and a variety of interactions from a multiple laser system]las been demonstrated, with WC:Co substrates. The process is conducted in open air and dots not involve hydrogen. Structural characterization of the diamond coatings. which have exceptional adhesion to cutting tool inserts. indicates a cubic diamond structure. Tungsten and cobalt atoms are incorporated into the film and a layer depleted in cobalt exists al the diamond-WC/Co interface. Electron field emission current densities. useful for flat panel displays of 6 mA/cm(2) at an applied voltage of 3000 V fora film-anode distance of 20 mu m has been measured. (C) 1998 Elsevier Science S.A.

Among wide-band-gap materials, diamond has been tested extensively in many laboratories for its applicability as an electron emission material. The results are encouraging but also point out the necessity of modifying the diamond films with respect to their chemical composition and/or atomic structure. This article reports on electron emission measurements conducted on diamond coatings deposited on WC/Co alloy by a multiple pulsed laser process. The electron emission has been measured in a diode configuration with a diamond surface–anode spacing of 20 and 50 μm in vacuum at P=10−7 Torr. Current densities of 6 mA/cm2 have been calculated at an applied voltage of 3000 V (for 20 μm). We propose an explanation for electron emission.

We describe herein a new process for the synthesis of diamond and diamond coated graphite fibers. The method uses mixtures of colloidal carbon and carbon fibers as the carbon source with metals and diamonds as seed or catalyst materials. The mixtures are reacted in a pure hydrogen microwave-assisted plasma at 900 °C for 20–22 h. The pre-existing fibers are fully coated with diamond on the surface with a graphite core as shown by Raman and scanning electron microscopy. In addition, various dendritic fibrous forms of diamond not found in chemical vapor deposition appear in several runs.

We describe herein a new process for the synthesis of diamond in the presence of various metals and atomic H in a microwave plasma. Along with the traditional high pressure high temperature (HPHT) process and the chemical vapor deposition (CVD) process, for diamonds synthesis this makes it a third route for this purpose. Starting materials used are intimate mixtures of various forms of carbon with one of many metals. These are exposed to a pure H2 microwave-assisted plasma at temperatures in the range 600–1100º C. Novel amorphous alloys are formed containing 40 to 70 atomic percent of carbon. From these liquid alloys diamonds are precipitated with temperature change and/or with possible evaporation of complex, hydrogen-rich Me−C−H species. The carbon content of the metallic liquid drops sequentially down to 5–6%C as more and more diamonds are precipitated therefrom. Au, Ag, Fe, Cu, Ni, and many other metals are used in most runs. Otherse.g. La, Mn, Sn, each give distinctive habits or morphology to the diamonds grown. Single crystals have been grown from these MexCyHz metallic liquids on natural diamond substrates, using the same low pressure solid state source (LPSSS) technique. They show high perfection. A mechanism is proposed quite analogous to the HPHT process, to explain this precipitation from metallic solutions, with atomic hydrogen ”substituting” for high pressure.

Electron field-emission tests have been performed on films grown by a modified microwave plasma assisted chemical vapor deposition diamond process. This modification includes the addition of N2 and O2 during the growth stage. Characterization of these films shows the presence of a disordered tetrahedral carbon structure. Raman spectroscopy indicates a disturbance in the cubic symmetry of the lattice and x-ray diffraction indicates a disordered tetrahedral structure. Field-emission testing indicate that current densities of 0.5 mA/cm2 can be obtained for applied fields of 5–8 V/μm. The results are explained in terms of a change in the band structure and the formation of electronic states in the band gap.

A new diamond deposition process utilizing a plasma and a variety of interactions from a multiple laser system has been demonstrated, with WCKo substrates. The process is conducted in open air and does not involve hydrogen. Structural characterization of the diamond coatings, which have exceptional adhesion to cutting tool inserts, indicates a cubic diamond structure. Tungsten and cobalt atoms are incorporated into the film and a layer depleted in cobalt exists at the diamond- WCKo interface. Electron field emission current densities reached 6mA/cm2 at an applied voltage of 3000V for a film-anode distance of 20pm. 1. QQC PROCESS

Real time spectroscopic ellipsometry has been applied to characterize the preparation of ∼2000-Å thick nanocrystalline diamond films on Si substrates by microwave plasma-enhanced chemical vapor deposition. Diamond films prepared under different conditions, including variations in the substrate temperature and CH4+H2+O2 gas mixture, have been studied. In addition to providing accurate Si substrate surface temperatures for diamond film growth via an ellipsometry-based calibration, the real time approach yields information on the following processes: (i) generation of initial substrate damage by the seeding process used to enhance diamond nucleation, (ii) annealing of the seeding damage that occurs upon heating the substrate to the deposition temperature, and (iii) the structural evolution of the diamond film throughout the nucleation and bulk film growth regimes. In the nucleation regime, the following information on the diamond film can be extracted: (i) the diamond mass thickness evolution with time, (ii) the sp2 C and void volume fractions in the nucleating layer, and (iii) the thickness at which nuclei make contact, the latter providing an estimate of the nucleation density. In the bulk layer growth regime, the time evolution of the following information can be extracted: (i) the bulk layer thickness, (ii) the surface roughness layer thickness, (iii) the mass thickness of sp2 C in the bulk layer, and (iv) the void volume fraction in the bulk layer. In the nucleation regime, we find that high quality diamond nanocrystals form under a wide range of gas compositions for substrate temperatures above 700°C. It is proposed that nucleation is controlled by a disordered carbon phase embedded in the substrate surface during the seeding process, in which the Si wafer is abraded with diamond powder. Above 700°C, the disordered C at the substrate surface is believed to recrystallize in the diamond phase upon exposure to an initial H2 plasma prior to diamond film growth. A common feature of diamond growth under all deposition conditions is the incorporation of a large concentration of sp2 C when diamond nuclei coalesce (typically after a thickness of 200–400 Å). The maximum concentration occurs under conditions for which poorer quality bulk films are obtained, including low substrate temperatures (<700 °C) and high CH4 flows ([CH4]/{[CH4]+[H2]} >0.02). The sp2 C is trapped within ∼300 Å of the substrate interface, but under optimum conditions of growth (i.e., the diamond growth region of the CHO gas phase diagram), little additional sp2 C forms with continued growth after the first 300 Å. The formation of sp2 C in the coalescence stage has been attributed to shadowing effects that lead to a reduction of atomic H relative to C-containing precursors arriving at shadowed surfaces. For the nanocrystalline diamond films studied here, it is found that films having the lowest volume fraction of sp2 C at the end of the 2000 Å deposition also exhibit the lowest void volume fraction and the smoothest surfaces.

We present evidence of the unique role of metallic liquids of composition MexCyHz (Me = Au, Ag, Cu, etc.) made by reacting mixtures of a metal and carbon in a microwave-stimulated H plasma at pressures near 100 Torr in diamond synthesis. Typical cubo-octahedral diamond crystals can be seen precipitating from such liquids in the temperature range 800–950 °C.

The growth of diamond thin films in enhanced chemical vapor deposition (CVD) processes requires high substrate temperatures (400–1000 °C) and gas pressures (1 Torr to 1 atm), as well as high-power excitation of the gas source (e.g., 1 kW microwave plasma). Thus determining the substrate temperature in this severe environment is a challenge. The issue is a critical one since substrate temperature is a key parameter for understanding and optimizing diamond film growth. We have developed and utilized methods for precise (∼±5 °C) Si substrate temperature calibration based on rapid-scanning spectroscopic ellipsometry. In this approach the E1 critical point energy in Si is used to deduce the temperature of the top ∼200 Å of the substrate. In addition, the broadening parameter associated with the critical point transitions can provide information on near-surface plasma damage. As an application of the temperature calibration, we have measured the kinetics of diamond film growth by the microwave plasma-enhanced CVD process.

We have applied real-time spectroscopic ellipsometry to monitor the growth of highly uniform, nanocrystalline diamond films by microwave plasma-enhanced chemical vapour deposition. In this study, a unique multichannel instrument is employed to collect full ellipsometric spectra from 1.5 to 4.0 eV. Here we focus on two capabilities. First, we will describe a method to calibrate the true temperature of the top 200Åof the Si substrate under diamond growth conditions. Second, we describe the full microstructural evolution of the diamond films. The parameters derived include the time evolution of the void and optically absorbing, non-diamond (sp2) carbon volume fractions in the film. In addition, the nuclei, bulk and surface roughness layer thicknesses during the nucleation, coalescence and bulk growth regimes are determined. These results reveal reproducible and remarkably internally consistent behaviour that provides new insights into the growth mechanisms for nanocrystalline diamond. We find that in the coalescence process, a large volume fraction of sp2 carbon is trapped in the grain boundaries under all conditions of growth. After coalescence is complete, further generation of sp2 carbon is impeded under optimum conditions.

The temperature dependence of the nucleation density of Chemical Vapor Deposition diamond was carefully investigated by ellipsometric monitoring. Substrates were pre-treated by rubbing with diamond powder and then by wiping off the residual powder until visually clean. Nucleation density was greater than 1010/cm2 in some ranges of temperature. It was also observed that nucleation density increased suddenly to 860°C and then gradually decreased in the range of higher temperatures. The results were explained by a change in the adsorption state of the precursor, from a physical to a chemical.

In-process monitoring of diamond film growth was performed with near-infrared ellipsometry (1550 nm). The trajectories in the ellipsometric parameters (ψ,Δ) differ according to the method of substrate pretreatment and the CO/H2 gas ratio used in the microwave plasma-enhanced chemical vapor deposition process. The nucleation density determined from ellipsometry shows qualitative agreement with that from scanning electron microscopy performed after deposition. The rate at which nuclei develop is also monitored, and the observed induction time is shorter for conditions leading to a higher nucleation density.