Diamond Ablators for Inertial Confinement Fusion

Applied Surface Science, 2001

The superb mechanical and electrical properties of diamond make it an attractive material for use in extreme conditions. Diamond devices have been fabricated, but the combination of diamond with other materials to form alloys is not yet wellunderstood. We have investigated the electrical and optical properties of diamond implanted with Si, which is in principle isoelectronic in diamond. The diamond layers were 23 mm thick p-type layers grown on Si(1 0 0) substrates. Silicon was implanted at room temperature, at energy of 300 keV with doses of up to 8:0 Â 10 16 cm À3 . A two-stage post-implant anneal process was then performed at 5008C for 30 min, then 8008C for 30 min. Rutherford backscattering spectrometry (RBS) measurements indicated Si concentrations up to 2 at.%, in agreement with simulations of implant pro®les. X-ray measurements indicated that about 60±70% of the Si was incorporated substitutionally, corresponding to up to 1.5 at.% from linear interpolation of lattice constants. Raman spectroscopy measurements con®rmed that the diamond structure was reconstructed with the post-implant anneal treatment. NEXAFS measurements con®rmed the reconstruction of the sp 3 diamond bonds from sp 2 graphite after annealing. Electrical measurements indicated an increase in diode current density with increased Si dose and a decrease in contact resistance with contact anneals. These novel diamond alloys may be useful for electronic and optical devices. We report on the preparation and properties of these alloys.

Plasma Processes and Polymers, 2007

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2015

Diamond is a unique material with robust mechanical properties, the electrical and the optical properties of the thin film diamond can be altered as they are deposited using microwave plasma enhanced chemical vapor deposition (MPCVD) method. The thin film diamond can be used both as optical window for certain wavelengths of light and as a reflector, based on the thickness and the deposition parameters of the thin film diamond. In this paper, we are illustrating a 1 µm thin film diamond that we were able to deposit, pattern and etch selectively using standard microfabrication techniques. This patterning of diamond film allows us to create 3D structures using single crystal diamond. I INTRODUCTION Diamond is a unique material, it is the hardest material identified with five times better heat conductor than copper. Diamond has a low coefficient of friction similar to Teflon and also has the lowest work function values [1-3]. About the optical properties, diamond has wide optical transitivity from the UV to the long IR range. About the electrical properties, diamond is an intrinsic electrical insulator with resistivity on the range of 10 14 to 10 16 ohm-cm and it is dope able with either an n-type or a p-type impurity to reach resistivity as low as 0.1 ohm-cm [2,3]. Diamond has a wide band gap energy level of 5.45 eV and it is chemically inert and biocompatible. These unique combination of diamond properties allows its use in a wide range of industrial applications. The superior quality of diamond among other materials is well known in optical, mechanical, thermal and electronic applications [4-6]. For several optical applications there is a need for a reflective optical surface, there is also need for diamond as stronger mechanical material for voltage converter, circuit breaker and other microsystems [4-7]. These microsystems with diamond as thin film can benefit from the versatile properties of the diamond. The diamond film deposited by microwave plasma enhanced chemical vapor deposition (MPCVD) can be manipulated during nucleation and growth conditions to achieve specific characteristics. It is meaningless determining an absolute quality for a diamond film without defining the ultimate application. For instance, optical windows require high transparency in the range of wavelength considered [8-10]. The transparency is linked to the diamond"s intrinsic quality (lowest amount of structural defects and impurities), as well as to roughness. The use of polycrystalline diamond film as a heat spreader also requires high intrinsic quality and a limited grain boundary network. However, mechanical applications do not need a very high crystallographic quality, but instead a high deformation resistance and sometimes a very low roughness. We in this paper present deposition of free standing thin film poly crystalline diamond that can be used for numerous application. II THIN FILM DIAMOND Diamond nucleation on non-diamond surfaces without pretreatment is usually very difficult and slow. Several studies reported in the literature [2-6,8], make clear the importance of control (and improvement) of nucleation and early stages of growth for application in which materials properties are sensitive to or directly dependent upon the morphology and the grain size. An increase in surface nucleation density should reduce morphological instabilities and associated surface roughness and further may improve the homogeneity of the film and reduce formation of voids at the substrate or coating interface, leading to better diamond-substrate adhesion and thermal transport properties [11]. Nucleation density has been increased from <10 5 cm-2 on untreated substrates up to 10 11 cm-2 on scratched or biased substrates. But there is still much debate and

Chemical Vapor Deposition, 2006

zation of ∼1.5 l B per f.u. for both bulk [5] and films. [21] The inset to shows a simple fit to a point contact Andreev reflection spectrum of a junction between a lead tip and the 340°C film, using the Blonder-Tinkham-Klapwijk (BTK) [22] model modified by Mazin et al. [23] in the diffusive regime, showing that the best fit gives a transport spin polarization of (85 ± 3) %.

MRS Proceedings, 2013

ABSTRACTPulsed electron beam ablation (15 keV, 1 kA, 100 ns) has been used to grow thin films of nanocrystalline diamond on silicon substrates. The films have been grown at room temperature and 150°C, and under argon as the working background gas at a pressure of about 4 mTorr. Visible reflectance spectroscopic analysis has shown films thickness to range between about 55 nm and 115 nm. Visible-Raman spectroscopic measurements have confirmed the presence of sp3 carbon bonds with a substantial fraction in the deposited films, and surrounded by a graphitic phase. The morphological features of the films have been assessed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The films surface is relatively smooth at room temperature and for low thickness, and becomes rougher at high temperature and for thicker films.

Proceedings of SPIE - The International Society for Optical Engineering, 2003

Vacuum, 2013

A multistep growth and masking method allowed developing windows with controlled geometry inside a silicon frame. In this paper, we present a new method to produce nanocrystalline diamond windows with thickness of about 200 nm to 40 mm, with different areas and shapes (circular, rectangular and rounded rectangle). The nanocrystalline diamond (NCD) films deposited on a silicon substrate (100) ptype, had a nucleation density of about 10 11 part/cm 2. Electrostatic self-assembly of nanodiamond seeds (4 nm powder) improved nucleation. Silicon anisotropic etching reveals the window geometry. The high nucleation density enabled smooth surfaces on both sides without the need for polishing the window. Pressure tests were performed in windows of varying thickness. The windows with thickness larger than 10 mm supported a pressure gradient of 1 atm.

Diamond and Related Materials, 2007

Spherical and hollow diamond microspheres have been fabricated by plasma coating diamond layers onto sacrificial porous silica spheres with subsequent chemical etching of the matrices. The diamond coatings have controllable micron scale apertures created by the coalescence of the contiguous diamond crystallites. Subsequent capillary-enhanced etching produced hollow diamond microspheres. The diamond microshell walls contain submicron scale channels which provided a route to rapid silica etching. The wall thickness is controllable in the range of 5%-20% of the shell diameter by control of the nucleation density and plasma deposition time. The diameters of the diamond microshells lie in the range between 30 μm and 40 μm. The diamond shells have been characterized by field emission scanning electron microscopy (FESEM) and by Raman spectroscopy.

Diamond is a unique material with robust mechanical properties, the electrical and the optical properties of the thin film diamond can be altered as they are deposited using microwave plasma enhanced chemical vapor deposition (MPCVD) method. The thin film diamond can be used both as optical window for certain wavelengths of light and as a reflector, based on the thickness and the deposition parameters of the thin film diamond. In this paper, we are illustrating a 1 µm thin film diamond that we were able to deposit, pattern and etch selectively using standard microfabrication techniques. This patterning of diamond film allows us to create 3D structures using single crystal diamond.