RADIATIVE SUBSTRATE HEATING FOR HIGH-T(C) SUPERCONDUCTING THIN-FILM DEPOSITION - FILM-GROWTH-INDUCED TEMPERATURE-VARIATION

We have examined the problem of substrate temperature changes during the growth of YBa2Cu3O7-x (YBCO) thin films on LaAlO3 when the substrate is radiatively heated. Substrate temperature variations sufficient to degrade film quality occur unless the heater temperature is controlled during growth. At a heater temperature of 900-degrees-C, the temperature of a LaAlO3 substrate was measured to be only 540-degrees-C, while a similar substrate with a 2000-angstrom YBCO film reached 640-degrees-C. The experimental data and calculations indicate that the heater temperature must be as high as 1240-degrees-C to heat LaAlO3 to 730-degrees-C, and must be decreased by over 200-degrees-C during the first 500 angstrom of film deposition to maintain a constant substrate temperature during film growth. This study shows the need for an in situ noncontact substrate temperature measurement technique.