Constructing oxide interfaces and heterostructures by atomic layer-by-layer laser molecular beam epitaxy

Advancements in nanoscale engineering of oxide interfaces and heterostructures have led to discoveries of emergent phenomena and new artificial materials. Combining the strengths of reactive molecular-beam epitaxy and pulsed-laser deposition, we show here, with examples of Sr 1+ x Ti 1- x O 3+δ , Ruddlesden–Popper phase La n +1 Ni n O 3 n +1 ( n = 4), and LaAl 1+ y O 3(1+0.5 y ) /SrTiO 3 interfaces, that atomic layer-by-layer laser molecular-beam epitaxy significantly advances the state of the art in constructing oxide materials with atomic layer precision and control over stoichiometry. With atomic layer-by-layer laser molecular-beam epitaxy we have produced conducting LaAlO 3 /SrTiO 3 interfaces at high oxygen pressures that show no evidence of oxygen vacancies, a capability not accessible by existing techniques. The carrier density of the interfacial two-dimensional electron gas thus obtained agrees quantitatively with the electronic reconstruction mechanism. Applied physics: New technique for oxide interfaces Recent advances in synthesizing and engineering oxide interfaces and heterostructures have provided a powerful strategy for creating new artificial structures exhibiting phenomena not possible in other materials form. Now Professor Xiaoxing Xi at Temple University from the US collaborates with researchers from the US, Italy and China showing a success in constructing oxides with well controlled stoichiometry and atomic layer precision. The central method—atomic layer-by-layer laser molecular beam epitaxy (ALL-Laser MBE)—is built upon the combined strengths of molecular beam epitaxy and pulsed laser deposition. It allows not only the growth of thin films of a Ruddlesden-Popper phase La 5 Ni 4 O 13 , but LaAlO 3 /SrTiO 3 interfaces. Remarkably, no oxygen vacancies are detected in the oxide interfaces because of the high oxygen pressures during the growth and the carrier density of the two-dimensional electron gas agrees with the electronic reconstruction mechanism.