Chemical doping is a dominating method for manipulating oxide two-dimensional electron gas (2DEG). However, enhancing the doping level while maintaining the metallic conduction remains a challenge, which limits detailed knowledge of 2DEG manipulation. Herein, we propose a concept of high-entropy heterointerface, which consists of a complex oxide (containing at least 5 elements) at either or both sides of the interface. By doubly doping Sr and Mn elements in the Nd and Al sites of NdAlO3, we grow Nd1−xSrxAl1−xMnxO3 (NSAMO) films onto SrTiO3 (STO) substrates to fabricate NSAMO/STO high-entropy heterointerfaces with different thicknesses (2–30 nm) and a wide range of doping ratios x (0.14–0.56). The 2DEG conducting behavior is maintained until x = 0.42, which is higher compared with similar studies. The varying x results in the coexistence of rich properties like a weak anti-localization (0.14–0.42), abnormal Hall effect (0.28 & 0.42), Lifshitz transition (0.42) and stable structure. These results confirm the potential of this strategy to tailor 2DEG in all-oxide interfaces.
The demand for advanced microwave dielectric ceramics for 5G base station filters drives the need for materials combining moderate permittivity, high quality factor (Q × f), and near-zero temperature stability (τf). This work investigates Ga2O3-doped SrTiO3–NdAlO3 (ST-NA) ceramics. The optimal base composition (0.5ST-0.5NA) achieves εr = 40.2, Q × f = 12,729 GHz, τf = 5.89 ppm/°C. To further enhance the microwave dielectric performance, Ga2O3 doping was introduced into the ST-NA ceramics. The substitution of Ga3+ for Ti4+ not only induces associated oxygen vacancy formation but also effectively suppressed the reduction of Ti4+ to Ti3+ during sintering, thereby reducing conduction loss, while the dielectric constant remained relatively stable. Consequently, 1.5% Ga2O3-doped ST-NA ceramic exhibited excellent overall microwave dielectric properties, with εr = 40.7, Q × f = 21,441 GHz, τf = 1.78 ppm/°C. These results demonstrate that Ga2O3-doped ST-NA ceramics are promising candidates for temperature-stable, low-loss microwave components in 5G and other high-frequency communication systems.
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