Photoluminescence in Raman Scattering: Effects of HfO2 Template Layer on Ultrananocrystalline Diamond (UNCD) Films Grown on Stainless Steel Substrates

The growth of polycrystalline diamond films can play an important role in industry if they can be grown on industrially used materials like aluminum (Al) or stainless steel (SS).   A critical issue related to the growth of ultrananocrystalline diamond (UNCD) thin films on metals like SS, in a Hydrogen rich environment like the one present during growth of UNCD films, is the diffusion of Hydrogen (H) into the SS substrate, as it has been observed in prior research, which results in hydride formation in the SS that induce brittleness in the SS substrate.  Several interface layers have been proposed described to avoid the H diffusion into the SS. However, HfO2 has not been explored.  The work reported here was focused on investigating the growth of UNCD films on commercially available SS substrates by using an interface layer of HfO2, which was found to be a good diffusion barrier for H to inhibit penetration into the SS substrate. The samples where characterized with SEM and Raman spectroscopy.  A photoluminescence (PL) effect, observed in the Raman scattering analysis, is present in all the samples.  The PL effect may be due to the interaction of the UNCD / HfO2 interface. and the SS substrate rather than UNCD film alone.  The novel result from the experiments described here, is the fact that it is possible to grow UNCD films on unseeded HfO2 layers on SS substrates.Keywords: Poly-crystalline diamond, photoluminescence, UNCD, Stainless Steel, Hafnium Dioxide

A Critical Analysis of Techniques and Basic Phenomena Related to Deposition of High Temperature Superconducting Thin Films

The processes involved in plasma and ion beam sputter-, electron evaporation-, and laser ablation-deposition of high temperature superconducting thin films are critically reviewed. Recent advances in the development of these techniques are discussed in relation to basic physical phenomena, specific to each technique, which must be understood before high quality films can be produced. Low temperature processing of films is a common goal for each technique, particularly in relation to integrating high temperature superconducting films with the current microelectronics technology. Research is now demonstrating that the introduction of oxygen into the growing film, simultaneously with the deposition of the film components, is necessary to produce as-deposited superconducting films at relatively low substrate temperatures

Development of a Robust, High Current, Low Power Field Emission Electron Gun for a Spaceflight Reflectron Time-of-Flight Mass Spectrometer

Carbon materials, including carbon nanotubes (CNTs) and nitrogen-incorporated ultrananocrystalline diamond (N-UNCD), have been of considerable interest for field emission applications for over a decade. In particular, robust field emission materials are compelling for space applications due to the low power consumption and potential for miniaturization. A reflectron time-of-flight mass spectrometer (TOF-MS) under development for in situ measurements on the Moon and other Solar System bodies uses a field emitter to generate ions from gaseous samples, using electron ionization. For these unusual environments, robustness, reliability, and long life are of paramount importance, and to this end, we have explored the field emission properties and lifetime of carbon nanotubes and nitrogen-incorporated ultrananocrystalline diamond (N-UNCD) thin films, the latter developed and patented by Argonne National Laboratory. We will present recent investigations of N-UNCD as a robust field emitter, revealing that this material offers stable performance in high vacuum for up to 1000 hours with threshold voltage for emission of about 3-4 V/lJm and current densities in the range of tens of microA. Optimizing the mass resolution and sensitivity of such a mass spectrometer has also been enabled by a parallel effort to scale up a CNT emitter to an array measuring 2 mm x 40 mm. Through simulation and experiment of the new extended format emitter, we have determined that focusing the electron beam is limited due to the angular spread of the emitted electrons. This dispersion effect can be reduced through modification of the electron gun geometry, but this reduces the current reaching the ionization region. By increasing the transmission efficiency of the electron beam to the anode, we have increased the anode current by two orders of magnitude to realize a corresponding enhancement in instrument sensitivity, at a moderate cost to mass resolution. We will report recent experimental and modeling results to describe the performance of a field emission electron gun as employed in the Volatile Analysis by Pyrolysis of Regolith (VAPoR) TOF-MS prototype

Estudio de láminas delgadas de diamantes policristalinos: estructura cristalina, enalce químicos de átomos de carbono y efectos en la concentración de portadores de cargas eléctricas

Las películas delgadas de diamantes no sólo exhiben las propiedades del diamante cristalino, también se pueden utilizar para desarrollar dispositivos electrónicos. Este estudio hace una comparación de tres diferentes estructuras cristalinas de láminas delgadas de diamantes que fueron producidas utilizando métodos de deposición con vapor químico con plasma producido por microondas o con filamentos calientes y la concentración de cargadores eléctricos. La estructura de enlaces químicos de los átomos en las muestras se analizó utilizando espectroscopia de Raman y la concentración de los portadores de cargas eléctricas se midió utilizando un sistema del efecto de Hall. La data muestra que hay una relación entre la estructura cristalina y los enlaces químicos de los átomos de carbono en las láminas con la concentración de portadores de cargas eléctricas. Las láminas que exhiben una estructura de diamante nanocristalino muestran alta concentración de portadores de cargas eléctricas. En el otro extremo, la lámina que exhibe una estructura de diamante microcristalino tiene la menor concentración de portadores de carga eléctrica. Las láminas llamadas ultra-nano-cristalinas UNCD están compuestas de granos de diamantes cristalinos de 2 a 5 nm y contiene una amplia red de bordes de grano con átomos de carbono unidos en la configuración de sp2. Estas láminas de UNCD exhiben la mayor concentración de portadores eléctricos del orden de 1018. Estas películas de UNCD potencialmente pueden ser desarrolladas en dispositivos electrónicos alternos de alta potencia eléctrica y alta temperatura

MEMS/NEMS based on mono-, nano-, and ultrananocrystalline diamond films

Diamond, because of its unique physical, chemical, and electrical properties and the feasibility of growing it in thin-fi lm form, is an ideal choice as a material for the fabrication of reliable, long endurance, microelectromechanical/nanoelectromechanical systems (MEMS/NEMS). However, various practical challenges, including wafer-scale thickness uniformity, CMOS compatibility, surface micromachining, and, more importantly, controlling the internal stress of the diamond fi lms, make this material more challenging for MEMS engineers. Recent advances in the growth of diamond fi lms using chemical vapor deposition have changed this landscape since most technical hurdles have been overcome, enabling a new era of diamond based MEMS and NEMS development. This article discusses a few examples of MEMS and NEMS devices that have been fabricated using mono-, nano-, and ultrananocrystalline diamond films as well as their performance

Synthesis and characterization of smooth ultrananocrystalline diamond films via low pressure bias-enhanced nucleation and growth

This letter describes the fundamental process underlying the synthesis of ultrananocrystalline diamond (UNCD) films, using a new low-pressure, heat-assisted bias-enhanced nucleation (BEN)/bias enhanced growth (BEG) technique, involving H2/CH4 gas chemistry. This growth process yields UNCD films similar to those produced by the Ar-rich/CH4 chemistries, with pure diamond nanograins (3–5 nm), but smoother surfaces (~6 nm rms) and higher growth rate (~1 µm/h). Synchrotron-based x-Ray absorption spectroscopy, atomic force microscopy, and transmission electron microscopy studies on the BEN-BEG UNCD films provided information critical to understanding the nucleation and growth mechanisms, and growth condition-nanostructure-property relationships

Are diamonds a MEMS\u27 best friend?

Next-generation military and civilian communication systems will require technologies capable of handling data/ audio, and video simultaneously while supporting multiple RF systems operating in several different frequency bands from the MHz to the GHz range [1]. RF microelectromechanical/nanoelectromechanical (MEMS/NEMS) devices, such as resonators and switches, are attractive to industry as they offer a means by which performance can be greatly improved for wireless applications while at the same time potentially reducing overall size and weight as well as manufacturing costs

Thermal transport and grain boundary conductance in ultrananocrystalline diamond thin films

Although diamond has the highest known room temperature thermal conductivity, k similar to 2200 W/m K, highly sp(3) amorphous carbon films have k \u3c 15 W/m K. We carry out an integrated experimental and simulation study of thermal transport in ultrananocrystalline diamond (UNCD) films. The experiments show that UNCD films with a grain size of 3-5 nm have thermal conductivities as high as k=12 W/m K at room temperature, comparable with that of the most conductive amorphous diamond films. This value corresponds to a grain boundary (Kapitza) conductance greater than 3000 MW/m(2) K, which is ten times larger than that previously seen in any material. Our simulations of both UNCD and individual diamond grain boundaries yield values for the grain boundary conductance consistent with the experimentally obtained value, leading us to conclude that thermal transport in UNCD is controlled by the intrinsic properties of the grain boundaries