Cation stoichiometry and electrical transport properties of the NdGaO₃/(0 0 1)SrTiO₃interface

Abstract

The interface formed between two wide band-gap insulators, NdGaO3 and SrTiO3 renders metallic behavior, similar to the LaAlO3/SrTiO3 interface. The interface conductivity depends strongly upon oxygen pressure during growth of the NdGaO3 film and subsequent annealing in oxygen. The conductivity of a (10 uc) NdGaO3/SrTiO3 film, pulsed laser deposited at low (pO2 = 10(-4) mbar) oxygen pressure, vanishes after annealing at 600 °C in oxygen atmosphere. For a similar interface formed at high oxygen pressure (pO2 = 0.3 mbar), the metallic conductivity remains also after post annealing. Medium energy ion spectroscopy (MEIS) in random (non-channeling) direction showed that a substantial part of Ga is missing in films deposited at low pressure, while optimal stoichiometry is approached in films deposited at high pressure. Aligned (channeling) MEIS likewise show that the Ga/Nd ratio approaches the stoichiometric value as the pressure is increased from 10(-4) to 0.3 mbar. This is interpreted as due to gallium desorption from a growing film at high temperature and low oxygen pressure while the re-evaporation of gallium is considerably suppressed at higher pressure. We discuss the possible role of stoichiometry on electrical transport properties.

Defect Control of Conventional and Anomalous Electron Transport at Complex Oxide Interfaces

“…This process is controlled via the growth temperature [32]. Oxidation of Ga enhances its thermal stability [52]. Therefore, we observe an increase of the Ga concentration in the NGO films with increasing growth pressure as revealed by x-ray photoemission spectroscopy.…”

“…Here, however, the total carrier density is primarily unchanged, so that we can exclude a severe effect of nonstoichiometry in our experiments. Nevertheless, we cannot exclude a minor effect caused by a variation of the Ga content in films grown at high p dep [52].…”

Воздействие механических напряжений на зарядовое состояние межфазной границы в гетероструктурах LaAlO-=SUB=-3-=/SUB=-/(001)SrTiO-=SUB=-3-=/SUB=- c нарушенной стехиометрией

“…На существенное влияние механических напряжений на зарядовое состояние межфазной границы в гетеро-структурах LAO/STO указывают данные о деградации их проводимости в процессе частичной аморфизации слоя алюмината лантана и восстановлении исходных значе-ний в процессе его вторичной рекристаллизации [15]. Следует отметить, что формирование прослойки с вы-сокой латеральной проводимостью межфазной границы наблюдалось [16] и при замене слоя лантана алюмината в гетероструктуре LAO/STO на слой из галата неоди-ма, параметр псевдокубической элементарной ячейки которого, как и параметр ячейки лантана алюмината меньше соответствующего параметра STO. Неодим, как и лантан, является донорной примесью в титанате стронция.…”

Review on fabrication methods of SrTiO3-based two dimensional conductive interfaces

“…Moreover, the STO with favorable stability hardly reacts with other materials, contributing to the formation of epitaxial heterointerfaces with various oxides (CaZrO3, EuO, GdTiO3, NdGaO3, and so on ). [18][19][20][21][22][23][24] In addition, the STO has been extensively applied in the fields of ferroelectric memory, pyroelectric and microwave-controlled devices etc. [25][26][27][28] The applications of these devices are mostly based on their high permittivity (300 F/m), low dielectric loss and high critical breakdown field.…”