Plasma Diagnostics for the Deposition of Nanomaterials (Alumina)

1. Summer REU in Nanomaterials and Nanomechanics May 29, 2008 Plasma Diagnostics for the Deposition of Nanomaterials (Alumina) Jay Mehta Undergraduate Student, University of Arkansas, Fayetteville, Arkansas 72701, USA Faculty Mentor: Dr. Matthew H. Gordon Associate Professor of Mechanical Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA Ph.D. Graduate Student Mentor: Sam Mensah Graduate Student, University of Arkansas, Fayetteville, Arkansas 72701, USA University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

2. Introduction • Desirable properties of alumina (Al2O3): • high melting temperature (2053 °C) • Considered best anti—oxidation coating at high temps • corrosion resistance • chemical inertness • High mechanical strength and hardness (24GPa) • transparency • Great insulating properties • Exceptional chemical and mechanical stability at temperatures above 1000 °C. • Alumina has several phases: γ-, η-, θ-, δ- , α- and κ-phases • Alpha phase is most desirable as it’s the most stable, has high hardness, and has limited change in volume with increasing temperature University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

3. Introduction • Alpha alumina films have many applications: • Optical coatings • Cutting tools • Biomedical implants • Thermal coatings • Dielectric films • Past work • coating cutting tools blades with alumina University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

4. Introduction • There are two different ways alpha alumina has been deposited: • Chemical Vapor Deposition (CVD) • Physical Vapor Deposition (PVD) • CVD is the traditional commercial approach • Done at temperatures above 1000 °C, limits substrates • When deposited at high temperatures, residual stresses in the film form • Results in weak coatings after heat treatment and questionable adhesion • Thus PVD at low temperatures is desired University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

5. Introduction • Many techniques for PVD: • electron beam evaporation • plasma spraying • gas detonation • laser ablation • RF sputtering • DC- and pulsed DC magnetron sputtering • midfrequency AC magnetron sputtering • Using midfrequency inverted cylinder AC magnetron sputtering through the Isoflux ICM 10 machine University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

6. Characterization of films • 3 techniques for characterizing films: • XRD: X-Ray Disfraction • SEM: Scanning Electron Microscopy • TEM: Transmission Electron Microscopy University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

7. Characterization of films • XRD: X-Ray Disfraction • Shoots x-rays into material at different angles and records feedback from the material • Each material has specific sets of “peaks” and the material can be identified by matching the XRD peaks University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

8. Characterization of films • SEM: Scanning Electron Microscopy • A microscope on the nano and micro scale • Uses electrons to create images vs. light • Can achieve much higher magnifications and resolutions up to a few nanometers University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

9. Characterization of films • TEM: Transmission Electron Microscopy • Used to transmit a beam of electrons through a very thin sample • Enables examination of a thin cross section • SAED on right used to identify phase (012 and 014 is alpha) 223 300 202 211 012 110 113 University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

10. Past Work • Previous years: • Attempted to grow alpha alumina on chromium oxide templates • Grew mixed phase alpha with gamma • This year: • Attempt to grow alpha alumina without template • Ran 39 recipes or combinations of variables to optimize the films University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

11. Problems to address and Goals • Confusing XRD results • Seek consultation with experts to characterize films with pole diagrams • Confusing TEM results • Believe we grew alpha, need to confirm • Will attempt to reassess on site • Thickness measurement • Need an accurate and nondestructive method for measuring thickness of films (lower priority b/c we aren’t sure of film type) • Optimize recipe for growing alumina • Experimentally run deposition with optical emission spectroscopy (OES) • Overall Goal: Better understanding of alpha alumina University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu