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Gallium oxide (Ga 2 O 3 ) thin films were deposited on a-Al 2 O 3 (11 20) substrates by pulsed laser deposition (PLD) with different oxygen pressures at 650 • C. By reducing the oxygen pressure, mixed-phase Ga 2 O 3 films with α and β phases can be obtained, and on the basis of this, mixed-phase Ga 2 O 3 thin film solar-blind photodetectors (SBPDs) were prepared. Comparing the responsivities of the mixed-phase Ga 2 O 3 SBPDs and the single β -Ga 2 O 3 SBPDs at a bias voltage of 25 V, it is found that the former has a maximum responsivity of approximately 12 A/W, which is approximately two orders of magnitude larger than that of the latter. This result shows that the mixed-phase structure of Ga 2 O 3 thin films can be used to prepare high-responsivity SBPDs. Moreover, the cause of this phenomenon was investigated, which will provide a feasible way to improve the responsivity of Ga 2 O 3 thin film SBPDs.

An approach to perform the multiple-scattering calculations of the two-cylinder acoustic scattering problem is studied here. The coupling factors and the analytical solutions of the poles are extracted by using the singularity expansion method (SEM). Through interpreting the coupling characteristic of the external oscillations, the poles are also obtained which are consistent with the exact results. It is noted that the coupling characteristic of the scattering field is the corresponding coupling between the oscillation modes of the same order, as well as the SEM poles. Based on this, we then infer that by interpreting the physical meaning of the coupling coefficients and explaining the influence of the coupling characteristic on the SEM poles, the pole distributions and the external oscillation characteristics of multiple scatterers can be studied in acoustic scattering problems. The study is based on general models, and then takes a two-same-cylinder model as an example for comparative analysis. In addition, the relationship between the real parts of the SEM poles and the separated distance is also analyzed briefly. The new approach and the related calculation results provide an effective way to perform shape recognition in the acoustic scattering field.

Mg x Zn 1−x O thin films were deposited on fused quartz substrate by PLD method with Mg 0.4 Zn 0.6 O source target, and the effect of the substrate surface atom constitution and the migration characteristics of reactive atoms on crystal structure of the MgZnO thin films were studied. Under oxygen-deficient condition, Mg x Zn 1−x O thin film deposited mainly along (200) orientation of cubic structure lattice at temperature below 350 °C because of the alternatively constituted substrate surface by Si and O atoms and the weak horizontal migration of reactive atoms, mix-constituted substrate surface(Si/O areas and O-rich areas) and the intense horizontal migration of reactive atoms introduced phase separation in Mg x Zn 1−x O thin films deposited at higher temperature. Single cubic structure (200) Mg 0.38 Zn 0.62 O thin films was made at 300 °C with Zn composition over theoretical limit in bulk materials, the band gap of which reached 4.2 eV and the MgZnO thin film could detect 330 nm near-UV light. And the available UV range of the cubic Mg x Zn 1−x O thin film deposited at 350 °C was widened to 348 nm near-UV light because of the cubic MgZnO grains with even higher Mg composition in this sample. Under high temperature and oxygen flow rate condition, Mg x Zn 1−x O thin film deposited mainly along the (200) orientation of cubic structure lattice at 2 Pa pressure, Mg x Zn 1−x O thin film deposited mainly along the (111) orientation of cubic structure lattice on O-rich substrate surface when the migration energy of reactive atoms is extremely small at 10 Pa oxygen pressure, and both mixconstituted substrate surface and medium migration energy of reactive atoms cause the phase separation occurred in Mg x Zn 1−x O thin films deposited under medium oxygen pressure. On the basis of the different substrate surface atom constitution and different migration characteristics of reactive atoms considering particular deposition method and condition, some previous results on the formation of different structure Mg x Zn 1−x O thin films and phase separation could also be interpreted. So the available UV range of cubic MgZnO thin film could be adjusted widely from near-UV (348 nm) to vacuum UV (<200 nm) range when both substrate surface atom constitution and migration characteristics of reactive atoms are suitable under given condition by multiple methods.

Mix-phase MgZnO thin film was fabricated on the c-plane sapphire substrate (Mg0.4Zn0.6O target) under high laser energy density condition by the PLD method. The internal quantum efficiency of the detector based on the mix-phase MgZnO thin film at 230 nm deep UV light reached 86% at 40 V bias voltage. And the Iuv(230 nm)/I dark ratio of the MgZnO detector reached 864 at 40 V bias voltage, which is mainly caused by both the higher internal gain of the detector at deep UV light and its smaller I dark . The high internal gain of the detector is mainly due to the higher density of interfaces between the different structure of MgZnO grains in the mix-phase MgZnO thin film, which is caused by the higher laser energy density deposition condition certified by contrast experiments. The small I dark of the detector is mainly caused by the higher barriers in the mix-phase MgZnO thin film and more cubic MgZnO in the mix-phase MgZnO thin film, and higher laser energy density deposition condition and O-rich c-plane sapphire substrate surface are key factors, which also agree with the contrast experiments results. So when the mix-phase MgZnO thin film that is constituted by both a small number of narrower band gap hexagonal MgZnO and a large number of wide band gap cubic MgZnO is used in the deep UV detector, and the difference in band gaps between different structures of MgZnO is relatively higher, a higher signal/noise ratio of the device at 230 nm deep UV light is gained, which is meaningful for developing high-performance deep UV detection technology.