Low Temperature Processing of Dielectric Thin Films

Chris Bratten

Rose-Hulman Institute of Technology

Mechanical / Biomedical Engineering

Advising Professors: Hugh Hillhouse and Elliott Slamovich

Introduction

Barium titanate (BaTiO3) is a piezoelectric material with a perovskite crystal structure. This material is showing much promise as a waveguide and optical switch with electro-optic response figures 10 to 100 times that of currently used materials. My research this summer focused on the hydrothermal synthesis of thin films of barium titanate.

Project Objectives

  • Produce thin films of barium titanate using the hydrothermal process
  • Use x-ray diffraction to verify formation of BaTiO3
  • Determine the dielectric properties using the microelectronics test bench

Experimental Approach

  • Cut standard glass slides in half to use as a substrate
  • Cleaned substrates in TCA, acetone, then methanol in a sonic bath
  • Deposited a thin film of titanium onto the substrates by evaporation
  • Made 1.0M and 0.5M solutions of Ba(OH)2 and 1.0M solutions of BaCl2 + NaOH
  • Placed samples in solution then backfilled containers with Ar gas
  • Heated in ovens for at least 24 hours at temperatures ranging from 65 to 90oC
  • Pulled out of solution in a nitrogen atmosphere glove box and rinsed with methanol to avoid the formation of barium carbonate
  • Used X-ray diffraction to determine how well the films formed barium Titanate
  • Best samples had titanium electrodes deposited using a TEM grid in the evaporator and were tested for capacitance and dielectric values

Research Findings

  • Ba(OH)2 solution produced consistently better films than the BaCl2 + NaOH solution
  • Higher temperatures produced better films than lower temperatures


X-Ray diffraction pattern of a hydrothermal BaTiO3 thin film.


Capacitance of the BaTiO3 film as a function of position.

Final Research Presentation