Direct Synthesis of Quasi-Single-Crystal Lithium Niobate Thin Films with High-Quality (006) Crystallinity and Ultrawide Bandgap via the Sol–Gel Method

Herein, high-quality (006)-oriented and ultrawide bandgap near-stoichiometric lithium niobate quasi-single crystal thin films are prepared using the sol–gel method. The optimal growth condition is investigated by changing the drying and annealing temperatures. The (006)-diffraction pattern of the X-ray diffraction spectra implies the high purity phase of the quasi-single crystal thin films. The molar ratio of the Li and Nb elements is analyzed using X-ray photoelectron spectroscopy and inductively coupled plasma mass spectrometry, confirming that the ratios close to 1:1 are measured. The bandgap of the lithium niobate is approximately 4.4 eV using the Tauc-plot fitting of the absorption spectra, and high-performance solar-blind photodetector based on the ultrawide bandgap lithium niobate thin films is studied. This work paves the way for advancing cost-effective optoelectronic devices based on lithium niobate thin films for UV detection technology.