研究目的
To examine the relationship between the crystalline quality and the electrical properties of ScN films grown on α-Al2O3(1102) substrates using molecular beam epitaxy, and to investigate the heteroepitaxial structure and factors determining electron mobility.
研究成果
Epitaxial ScN films on α-Al2O3(1102) show a specific orientation relationship with small anisotropy and tilt growth. Crystallinity improves with temperature and Sc-rich conditions, but highest electron mobility is achieved at a boundary condition balancing crystallinity and nonstoichiometry. Increased carrier scattering from ionized donors in Sc-rich conditions reduces mobility despite better crystallinity.
研究不足
The study is limited to specific growth conditions (temperature and Sc/N ratio) on α-Al2O3(1102) substrates; other substrates or methods not explored. The tilt growth mechanism is attributed to substrate atomic arrangement but not fully quantified. Electrical properties may be influenced by impurities not controlled.
1：Experimental Design and Method Selection:
ScN films were grown on α-Al2O3(1102) substrates using metal source molecular beam epitaxy (MBE) with an RF radical source for nitrogen. The study varied growth temperature (Tg) from 750°C to 900°C and Sc source temperature (TSc) from 1300°C to 1325°C to investigate effects on crystalline quality and electrical properties.
2：Sample Selection and Data Sources:
α-Al2O3 single crystals with (1102) faces were used as substrates. Substrates were heated at 900°C for 30 min for cleaning before growth.
3：List of Experimental Equipment and Materials:
Equipment includes an MBE system with RF radical source (13.56 MHz), Knudsen cell for Sc flux, X-ray diffractometer (X'Pert MRD, Malvern Panalytical Ltd.), transmission electron microscope (H-9000UHR, Hitachi High-Technologies Corp.), atomic force microscope (SPA-400, SII Nanotechnology Inc.), surface profiler (Dektak 3030, Sloan Technology Corp.), Hall effect measurement system (ResiTest 8200, TOYO Corp.), and spectrophotometer (SolidSpec-3700, Shimadzu Corp.). Materials include nitrogen gas (99.99995%), scandium (99.9%), and aluminum for contacts.
4：56 MHz), Knudsen cell for Sc flux, X-ray diffractometer (X'Pert MRD, Malvern Panalytical Ltd.), transmission electron microscope (H-9000UHR, Hitachi High-Technologies Corp.), atomic force microscope (SPA-400, SII Nanotechnology Inc.), surface profiler (Dektak 3030, Sloan Technology Corp.), Hall effect measurement system (ResiTest 8200, TOYO Corp.), and spectrophotometer (SolidSpec-3700, Shimadzu Corp.). Materials include nitrogen gas (99995%), scandium (9%), and aluminum for contacts. Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Substrates were cleaned by heating. Films were grown with nitrogen plasma irradiation, varying Tg and TSc. Thicknesses ranged from 140 to 300 nm. Structural analysis used XRD (θ–2θ, rocking curve, pole figure, reciprocal space mapping), TEM, AFM. Electrical properties measured by Hall effect with van der Pauw method. Optical properties evaluated by transmittance measurement.
5：Data Analysis Methods:
XRD data analyzed for orientation, tilt angle, FWHM. TEM and AFM for morphology. Hall effect data for resistivity, carrier concentration, mobility. Statistical analysis of dependencies on growth parameters.
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X-ray diffractometer
X'Pert MRD
Malvern Panalytical Ltd.
Analyze structure and crystallinity of films using XRD measurements in θ–2θ, rocking curve, pole figure, and reciprocal space mapping modes.
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Transmission electron microscope
H-9000UHR
Hitachi High-Technologies Corp.
Observe cross-sectional images of ScN films to study interface and dislocations.
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Spectrophotometer
SolidSpec-3700
Shimadzu Corp.
Evaluate optical properties by regular transmittance measurement.
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Atomic force microscope
SPA-400
SII Nanotechnology Inc.
Evaluate surface morphologies of films and substrates.
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Surface profiler
Dektak 3030
Sloan Technology Corp.
Measure thicknesses of the films.
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Hall effect measurement system
ResiTest 8200
TOYO Corp.
Determine electrical resistivity, carrier concentration, and mobility using van der Pauw method under magnetic field.
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Knudsen cell
K-cell
Supply Sc flux during film growth, using boron nitride crucible.
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RF radical source
Generate nitrogen plasma for nitrogen source in MBE growth.
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