A field-effect transistor in which the ferroelectric lithium niobate (LiNbO3) replaces the oxide in a conventional metal-oxide-semiconductor transistor has been fabricated. The channel conductance of this device has been shown to be strongly affected by the application of voltage pulses between the gate of the device and the substrate. A reduction of channel current of nearly 140 μA was observed after the application of a voltage pulse of −30 V and partially restored with a+10-V pulse. This behavior was found to be consistent with the influence of the polarization charge of the LiNbO3 layer on the carriers in the channel. This is the first observation of such behavior in a metal-ferroelectric-semiconductor field-effect transistor without the growth of a buffer layer between the semiconductor and ferroelectric to prevent charge injection.
The deposition of thin films of lithium niobate (LiNbO3) on silicon with rf magnetron sputtering has been investigated. A matrix of experiments was designed to determine the effect of several parameters on the resulting film quality. Under optimized conditions, oriented polycrystalline films of LiNbO3 are produced that exhibit a columnar grain structure with the polar axis normal to the substrate surface. Deviations from sputtering parameters optimized for producing LiNbO3, have been shown to produce films of varying proportions of either LiNb3O8 or Li3NbO4 with LiNbO3. The stoichiometry, microstructure, and electrical properties of selected films have been investigated with Rutherford backscattering, diffractometry, transmission electron microscopy, and a variety of electrical measurement techniques.
We report what is to our knowledge the first successful attempt in prism coupling a laser beam into a lithium niobate optical waveguide grown on a thermally oxidized (100) Si substrate by magnetron rf sputtering. Bragg x-ray diffraction, Rutherford backscattering, and birefringence measurements confirm that the sputtered films were nearly stoichiometric as well as highly textured lithium niobate. The refractive indices were n(TE) = 2.199 +/- 0.002 and n(TM) = 2.263 +/- 0.002. The lowest propagation loss in the waveguide was determined to be 1.9 +/- 0.1 dB/cm at a wavelength of 633 nm.
A technique combining metalorganic decomposition and rf sputtering is used to grow lithium niobate (LiNbO3) thin films on diamond/silicon substrates, and surface acoustic wave (SAW) filters are fabricated by depositing interdigital transducers onto the multilayer LiNbO3/diamond/silicon structures. Microwave characterization is achieved by using a network analyzer. Evidence is found for SAW propagation in these structures. These experimental findings agree with theoretical predictions.
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