Compact laser molecular beam epitaxy system using laser heating of substrate for oxide film growth

Abstract

A high-temperature, oxygen compatible, and compact laser molecular beam epitaxy (laser MBE) system has been developed. The 1.06 μm infrared light from a continuous wave neodymium-doped yttrium aluminum garnet (Nd:YAG) laser was used to achieve a wide range and rapid control of substrate temperature in ultrahigh vacuum and at up to 1 atm oxygen pressure. The maximum usable temperature was limited to 1453 °C by the melting point of the nickel sample holder. To our knowledge, this is the highest temperature reported for pulsed laser deposition of oxide films. The efficient laser heating combined with temperature monitoring by a pyrometer and feedback control of the Nd:YAG laser power by a personal computer made it possible to regulate the substrate temperature accurately and to achieve high sample heating and cooling rates. The oxygen pressure and ablation laser triggering were also controlled by the computer. The accurate growth parameter control was combined with real-time in situ surface structure monitoring by reflection high energy electron diffraction to investigate oxide thin film growth in detail over a wide range of temperatures, oxygen partial pressures, and deposition rates. We have demonstrated the performance of this system by the fabrication of homoepitaxial ${\mathrm{SrTiO}}_{\mathrm{3}}$ films as well as heteroepitaxial ${\mathrm{Sr}}_{\mathrm{2}}{\mathrm{RuO}}_{\mathrm{4}},$ and ${\mathrm{SrRuO}}_{\mathrm{3}}$ films on ${\mathrm{SrTiO}}_{\mathrm{3}}$ substrates at temperatures of up to 1300 °C. This temperature was high enough to change the film growth mode from layer by layer to step flow.