本研究利用射頻磁控濺鍍沉積氧化鎵、氧化鋅及二氧化錫薄膜作為晶種層，並利用水熱法於各晶種層薄膜中進行氧化鎵奈米柱的成長，並討論各種退火溫度對其奈米柱形貌及結構的影響，以及其作為感測層，用於深紫外光感測器之特性。
首先，利用射頻磁控濺鍍沉積氧化鎵薄膜200奈米。由於氧化鎵在300℃以上退火，會從GaOOH轉相成α-氧化鎵，在650℃以上則會轉化成最穩定的β-氧化鎵。於是我們分別將其退火溫度控制在600、700、800及900℃。透過XRD分析，確認其晶體結構成功轉相，並將其製備成深紫外光感測器。隨著退火溫度增加，感測器的光電流也隨之增加，並在700℃退火的氧化鎵薄膜得到最大1.859 × 10^-9安培的光電流，退火溫度大於800℃後，光電流和暗電流則都下降到10^-13安培左右或更小。
接著，我們選擇以退火900℃的氧化鎵薄膜作為晶種層，以防止晶種層電流對氧化鎵奈米柱電性的影響。以水熱法在其表面成長前驅物GaOOH奈米柱，再分別以600、700、800及900℃進行退火。700℃退火下，得到最佳的β-氧化鎵奈米柱紫外光感測器，響應值為2.586×10^-7 (A/W)，光暗電流比為2.883倍。於是，我們接下來也會以退火700℃的氧化鎵奈米柱成長於氧化鋅及二氧化錫晶種層上。
氧化鋅薄膜於退火溫度600℃時有最好的結晶度及最小的晶體尺寸，這也使得其上層所成長的氧化鎵奈米棒也同時有最小的奈米棒尺寸及最高的分布密度。這項優勢也展現在其所製成的紫外光感測器中，響應值高達3.879×10^-1 (A/W)及光暗電流比4.118倍，都高於氧化鎵薄膜做為晶種層所成長出的奈米柱。
最後，我們探討以二氧化錫薄膜做為晶種層成長氧化鎵奈米柱。透過XRD分析及SEM圖可以發現，退火400℃以上的二氧化錫薄膜，由於其晶格參數c=3.18(Å)更接近前驅物氫氧氧鎵晶格參數b=2.98(Å)，二氧化錫的(200)晶面與GaOOH的(002)晶面之間良好的晶格匹配，使奈米棒能夠朝向平行c軸方向優選成長，長成較短但密度極高的奈米棒陣列，這也使其製成的紫外光感測器有著極為優異的感測性能。以未退火的二氧化錫做為晶種層的氧化鎵奈米柱紫外光感測器響應值為5.647×10^-2(A/W)，光暗電流比高達348.5倍，退火400℃以上的二氧化錫做為晶種層，也都有至少69.1倍的光暗電流比，遠高於氧化鎵及氧化鋅晶種層。

This study focuses on the synthesis of gallium oxide (Ga2O3) nanorods using a hydrothermal method on seed layers deposited via radio-frequency magnetron sputtering of Ga2O3, zinc oxide (ZnO), and tin dioxide (SnO2) thin films. We investigate the impact of different annealing temperatures on the morphology, structure, and properties of the resulting nanorods, as well as their suitability as sensing layers for deep ultraviolet photodetectors.
Initially, Ga2O3 thin film with a thickness of 200 nanometers were deposited using radio-frequency magnetron sputtering. Ga2O3 exhibits phase transitions upon annealing, converting from amorphous to α-Ga2O3 at temperatures exceeding 300°C, and ultimately to the stable β-Ga2O3 at temperatures above 650°C. We controlled the annealing temperatures at 600°C, 700°C, 800°C, and 900°C, with X-ray diffraction (XRD) confirming successful structural phase transitions. Ultraviolet photodetectors were fabricated using these films. As the annealing temperature increased, the photodetectors exhibited elevated photocurrents, with the highest value of 1.859×10^-9 amperes obtained for Ga2O3 films annealed at 700°C. After annealing temperatures exceeded 800°C, both the photocurrent and dark current decreased to approximately 10^-13 amperes or lower.
Subsequently, we selected Ga2O3 thin films annealed at 900°C as seed layers to minimize their impact on the electrical properties of Ga2O3 nanorods. Hydrothermal growth was employed to fabricate precursor GaOOH nanorods on the seed layer, followed by annealing at 600°C, 700°C, 800°C, and 900°C. The best results were observed for the β-Ga2O3 nanorods photodetectors annealed at 700°C, which exhibited a responsivity of 2.586×10^-7 (A/W) and a response ratio of 2.883. In our ongoing research, we plan to explore the growth of Ga2O3 nanorods on ZnO and SnO2 seed layers using the 700°C-annealed Ga2O3 nanorods as a reference.
ZnO thin film annealed at 600°C displayed excellent crystallinity and minimal crystal size, leading to the growth of Ga2O3 nanorods with reduced dimensions and higher density. This advantage was evident in the resulting ultraviolet photodetectors, which exhibited a high responsivity of 3.879×10^-1 (A/W) and a response ratio of 4.118. These values surpassed those obtained using Ga2O3 thin film as seed layer for nanorods growth.
Finally, we investigated the growth of Ga2O3 nanorods on SnO2 seed layer. XRD and SEM analyses revealed that SnO2 thin film annealed at temperatures exceeding 400°C exhibited a polycrystalline structure. The lattice parameters of SnO2 (c=3.18 Å) closely matched those of the precursor GaOOH (b=2.98 Å), promoting the preferential growth of nanorods along the c-axis. These formed shorter but highly dense nanorods arrays, leading to the development of exceptional ultraviolet photodetectors. Specifically, photodetectors fabricated with as-deposited SnO2 seed layer exhibited a responsivity of 5.647×10^-2 (A/W) and a remarkable response ratio of 348.5. For annealing SnO2 seed layer exceeding 400°C, the resulting Ga2O3 nanorods photodetectors exhibited a response ratio of at least 69.1, which significantly surpasses those obtained with Ga2O3 and ZnO seed layer.

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