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In-Situ Diagnostics for Metalorganic Chemical Vapor Deposition of YBCO


Tripathi, Ashok Burton (2001) In-Situ Diagnostics for Metalorganic Chemical Vapor Deposition of YBCO. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/3ZJS-BE38.


A new stagnation flow MOCVD research reactor is described that is designed to serve as a testbed to develop tools for "intelligent" thin film deposition, such as in-situ sensors and diagnostics, control algorithms, and thin film growth models. The reactor is designed in particular for the deposition of epitaxial YBa2Cu3O7-δ on MgO, although with minor modifications it would be suitable for deposition of any metal-oxide thin films.

The reactor is specifically designed to permit closed-loop thermal and stoichiometric control of the film growth process. Closed-loop control of precursor flow rates is accomplished by using ultraviolet absorption spectroscopy on each precursor line. Also integrated into the design is a Fourier Transform Infrared (FTIR) spectroscopy system which collects real-time, in-situ infrared polarized reflectance spectra of the film as it grows. Numerical simulation was used extensively to optimize the fluid dynamics and heat transfer to provide uniform fluxes to the substrate. As a result, thickness uniformity across the substrate is typically within 3% from the center to the edge of the substrate.

Experimental studies of thin films grown in the Y/Ba/Cu/O system have been carried out. The films have been characterized by Rutherford Backscattering Spectrometry and X-ray Diffraction. Results indicate c-axis oriented grains with pure 1:2:3 phase YBCO, good spatial uniformity, and a low degree of c-axis wobble. Experimental growth data is used in a gas phase and surface chemistry model to calculate sticking coefficients for yttrium oxide, barium oxide, and copper oxide on YBCO.

In-situ FTIR and Coherent Gradient Sensing (CGS) analysis of growing films has been performed, yielding accurate substrate temperature, film thickness monitoring, and full-field, real-time curvature maps of the films. In addition, we have implemented CGS to obtain full-field in-situ images of local curvature during oxygenation and deoxygenation of YBCO films. An analysis of the oxygen diffusion is performed, and diffusivity constants are presented for a variety of temperature and film conditions.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Mechanical Engineering and Materials Science)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Mechanical Engineering
Minor Option:Materials Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Goodwin, David G.
Thesis Committee:
  • Goodwin, David G. (chair)
  • Bhattacharya, Kaushik
  • Hunt, Melany L.
  • Murray, Richard M.
  • Raja, L.
Defense Date:26 February 2001
Record Number:CaltechETD:etd-09262005-143545
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3785
Deposited By: Imported from ETD-db
Deposited On:28 Sep 2005
Last Modified:30 Aug 2022 22:11

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