MBE Growth of High Tc Superconductors

Thermodynamics of the Mg–B system: Implications for the deposition of MgB2 thin films

“…By converting the Mg vapor pressure to Mg flux from the deposition source using the formulism described in Ref. [18], the film deposition parameters can then be determined. For example, at the optimum temperature of about 1350 K the Mg vapor pressure has to be in the range of 10 Torr, which is highly impossible for many film deposition techniques.…”

The Importance of In Situ Monitors in the Preparation of Layered Oxide Heterostructures by Reactive MBE

“…Achieving such composition control has been a major problem in prior oxide MBE work [15]. We have met this challenge using a combination of AA (calibrated in situ using a QCM) and by monitoring the RHEED intensity oscillations that occur during the monolayer-bymonolayer deposition of SrTiO 3 and BaTiO 3 calibration layers.…”

Growth of SrTiO3(110) film by oxide molecular beam epitaxy with feedback control

“…There are steps with the height of a single unit cell on the surface corresponding to the layer-by-layer growth of the SrTiO atomic plane. And the area ratio of the higher terraces indicates the amount of the growing layer, i.e., ∼0.1 ML at t 4 and ∼0.6 ML at t 5 . While the step roughness changes dramatically, the high-resolution STM images show no detectable change of the area ratio of (5×1) and (4×1) reconstructions, i.e., the surface stoichiometry almost keeps unchanged.…”

“…2 Unlike the adsorption and incorporation processes during GaAs film growth in which only one low vapor pressure element Ga is involved and the stoichiometry can be obtained within the self-regulation mechanism, 3,4 the OMBE growth of complex oxide films involves multiple low vapor pressure metals and therefore requires precise flux control of each individual evaporating beam. [5][6][7][8] The in situ quartz crystal microbalance (QCM) or atomic absorption spectroscopy (AAS) technique offers a few percent precision for the calibration of the flux rates of metal sources.…”

“…[5][6][7][8] The in situ quartz crystal microbalance (QCM) or atomic absorption spectroscopy (AAS) technique offers a few percent precision for the calibration of the flux rates of metal sources. 4 However, the optimization of OMBE growth with QCM or AAS has to be based on the assumption that adhesion coefficient of the evaporating species keeps the same on the growing surface and the quartz crystal regardless their temperature difference. It is not always true in the real OMBE growth, so the stoichiometry precision of the film is deteriorated.…”