研究目的
To describe the structure and microtexture of MgO and Mg-doped ZnO layers grown by ALD on α-Al2O3 and GaN substrates using TEM and electrical measurements, focusing on the influence of buffer layer orientation on thin-film microstructure.
研究成果
MgO grows epitaxially on α-Al2O3 and GaN with defects, transforming to random orientation. For 10 at% Mg doping, an MgO buffer layer forms, aiding epitaxial ZnO growth on α-Al2O3 with improved mobility, while on GaN, ZnO is textured. α-Al2O3 is better for high Mg doping. For 1 at% Mg doping, successful incorporation occurs on GaN, but MgO forms on α-Al2O3, indicating substrate dependence for low-concentration doping.
研究不足
The solid solubility of MgO in ZnO is limited to 4 at% maximum, which may restrict doping levels. The study is focused on specific substrates and ALD conditions; results may not generalize to other growth methods or substrates. TEM analysis is localized and may not represent the entire sample uniformly.
1：Experimental Design and Method Selection:
Atomic layer deposition (ALD) was used to grow pure MgO and Mg-doped ZnO layers with 1 at% and 10 at% Mg concentrations on (001)-oriented α-Al2O3, (001) GaN, and (110) Si substrates at 300°C without annealing. Transmission electron microscopy (TEM), including selected area electron diffraction (SAED), high-resolution TEM (HRTEM), and energy dispersive spectroscopy (EDS), was employed to study structure and microstructure. Electrical properties were measured using Hall measurements in Van der Pauw configuration.
2：Sample Selection and Data Sources:
Substrates were (001) α-Al2O3, (001) GaN, and (110) Si. α-Al2O3 and GaN substrates were cleaned with concentrated HNO3 and 18 MΩ DI water. Samples were grown with different Mg concentrations (0 at%, 1 at%, 10 at%, and 100 at% Mg).
3：List of Experimental Equipment and Materials:
ALD reactor (Picosun SUNALE R-100), precursors (diethylzinc (DEZ), bis(ethylcyclopentadienyl)magnesium (Mg(CpEt)2), DI water), carrier gas (nitrogen), TEM microscopes (Philips CM20, JEOL 3010, THEMIS with Super-X EDS detector), Hall measurement setup, Dektak profilometer, UV-VIS spectrometer.
4：Experimental Procedures and Operational Workflow:
ALD deposition at 300°C with specific pulse and purge times. Mg doping by inserting Mg precursor pulses among Zn precursor pulses. Electrical measurements with In contacts. Thickness measurement with profilometer. TEM sample preparation and analysis including SAED, HRTEM, EDS mapping.
5：Data Analysis Methods:
Electrical parameters calculated from Hall measurements. Bandgaps calculated from UV-VIS absorption. TEM images and diffraction patterns analyzed for crystal structure and orientation. EDS for elemental composition.
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