Chemically reduced lithium niobate single crystals: Processing, properties and improved surface acoustic wave device fabrication and performance

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Lithium niobate single-crystal wafers were chemically reduced using nitrogen/hydrogen atmospheres at a variety of temperatures between 350 and 750 °C. Reduced wafers were measured to have increased optical absorptivity and increased direct current (dc) electrical conductivity as a function of reduction-processing temperature. Absorptivity increases were measured larger than 1000×; conductivity could be increased by more than a factor of 105. Standard 78 MHz surface acoustic wave (SAW) filters were successfully fabricated using reduced wafers, and shown to have increased resistance to spurious pyroelectric charging effects during thermal cycling. The observed increases in optical absorptivity and dc electrical conductivity can also be expected to provide benefits for SAW device fabrication processing.