Spin-polarized Wide Electron Slabs in Functionally Graded Polar Oxide Heterostructures

Abstract

We report on the high mobility wide electron slabs with enhanced correlation effects by tailoring the polarization effects in a functionally graded ZnMgO/ZnO heterostructures. The characteristics of three-dimensional (3D) spreading electrons are evidenced by the capacitance-voltage profiling and the quantization of 3D Fermi surface in magneto-transport measurements. Despite the weak spin-orbit interaction, such electron slabs are spin-polarized with a large zero-field spin splitting energy, which is induced by the carrier-mediated ferromagnetism. Our results suggest that the vast majority of electrons are localized at the surface magnetic moment which does not allow spin manipulations, and only in the region visited by the itinerant carriers that the ferromagnetic exchange interactions via coupling to the surface local moments contribute to the spin transport. The host ferromagnetism is likely due to the formation of Zn cation vacancies on the surface regime induced by the stabilization mechanism and strain-relaxation in ZnMgO polar ionic surface.

Defect-induced magnetism in SiC: Interplay between ferromagnetism and paramagnetism

“…Both Zn and O vacancies have been suggested to be responsible for the induced magnetism [18,[60][61][62]. On the other hand, oxygen atoms on the polar ZnO surface can be spin polarized and undergo a long-range magnetic interaction [63][64][65]. in Fig.…”

Polarization discontinuity induced two-dimensional electron gas at ZnO/Zn(Mg)O interfaces: A first-principles study

“…23 Recently, a different type of system supporting a 2DEG, wurtzite ZnO/Zn(Mg)O heterostructures, has been investigated experimentally. [24][25][26][27][28][29][30][31][32] These heterostructures are usually grown using molecular beam epitaxy; 24,25 however, a 2DEG was also demonstrated in samples grown with metal-organic vapor deposition which is suitable for mass production. 30,31 The presence of the 2DEG is normally confirmed by Hall effect and capacitance measurements.…”

“…[24][25][26][27][28][29][30][31][32] These heterostructures are usually grown using molecular beam epitaxy; 24,25 however, a 2DEG was also demonstrated in samples grown with metal-organic vapor deposition which is suitable for mass production. 30,31 The presence of the 2DEG is normally confirmed by Hall effect and capacitance measurements. 24,27,28 The observation of the quantum Hall effect 25 and the fractional quantum Hall effect 29 in these heterostructures testifies to the high quality of these interfaces.…”

Interfacial and bulk polaron masses in Zn1−xMgxO/ZnO heterostructures examined by terahertz time-domain cyclotron spectroscopy

“…The PL spectra of the Zn 1−x Mg x O layers are broad as a result of compositional grading. 11 No excitonic PL emission was witnessed from the Zn 1−x Mg x O layers, which may be a result of electric-field-induced exciton dissociation 13 in the surface electric field of Zn 1−x Mg x O.…”

“…26,27 The Zn 1−x Mg x O/ZnO heterostructures studied herein were found to be spin polarized and to exhibit weak ferromagnetism. 11,28 However, the magnetization saturated at B = 0.4 T, and the degree of spin-polarization should therefore not alter at the magnetic field strengths B > 1 T used in the CR experiments.…”