In-plane anisotropy in two-dimensional electron gas at LaAlO_3/SrTiO_3(110) interface

A systematic study of the two-dimensional electron gas at La AlO_3/SrTiO_3（110） interface reveals an anisotropy along two specific directions, [001] and 1ī0. The anisotropy becomes distinct for the interface prepared under high oxygen pressure with low carrier density. Angular dependence of magnetoresistance shows that the electron confinement is stronger along the 1ī0 direction. Gate-tunable magnetoresistance reveals a clear in-plane anisotropy of the spin–orbit coupling,and the spin relaxation mechanism along both directions belongs to D＇yakonov–Perel＇（DP） scenario. Moreover, in-plane anisotropic superconductivity is observed for the sample with high carrier density, the superconducting transition temperature is lower but the upper critical field is higher along the 1ī0 direction. This in-plane anisotropy could be ascribed to the anisotropic band structure along the two crystallographic directions.

Wet nitrogen oxidation technology and its anisotropy influence on VCSELs

Vertical cavity surface emitting lasers（VCSELs） are widely used in optical communications and optical interconnects due to their advantages of low threshold, low power consumption and so on. Wet nitrogen oxidation technology, which utilizes H20 molecules to oxidize the Al;Ga;As, is used for electrical and optical mode confinement. In this paper, the effects of oxidation time, oxidation temperature and oxidation anisotropy on the oxidation rate are explored and demonstrated. The ratio of oxidation rate on [0-11] to [011] crystal orientation is defined as oxidation anisotropy coefficient, which decreases with the increase of oxidation temperature and oxidation time. In order to analyze the effect of the oxidation anisotropy on the VCSEL performance, an oxide-aperture of the VCSELs with two difference shapes is designed and then fabricated. The static performance of these fabricated VCSELs has been measured,whose threshold current ratio ～0.714 is a good agreement with that of the theoretical calculation value ～0.785. Our research on wet nitrogen oxidation and its anisotropy serves as an important reference in the batch fabrication of large-area VCSELs.

Tailoring thermal conductivity of bulk graphene oxide by tuning the oxidation degree

Bulk graphene oxide （GO） shows great potential in a variety of applications, such as sensors,photodetectors, supercapacitors, lithium ion batteries and catalysts. However, its thermal conductivity,one of the most important and fundamental physical properties, is still less known. Herein, we havesystematically investigated the thermal conductivity of bulk GOs and find that it can be tailored by tuningtheir oxidation degree during preparation process. Notably, the cross-plane thermal conductivity of bulkGO, in comparison with its precursor graphite, exhibits more than 100 times decrease at roomtemperature. The dependence of thermal conductivity of GO on oxidation degree is attributed to thechemical and structural changes by introducing oxygen atoms and oxygen-containing functional groups,which can lead to a significant enhancement in atomic- and nano-scale phonon scattering. Furthermore,we reveal that the thermal conductivity of bulk GOs exhibits evident anisotropic behavior. These resultsprovide fundamental understanding and valuable information on thermal transport properties of bulkGOs for various practical applications.