Properties of Lithium Niobate Thin Polycrystalline Films Deposited on Silicon Substrates

Abstract

Thin films of LiNbO, approximately 1 p n in thickness have been r-f sputtered onto single crystal silicon substrates. X-ray diffraction studies have confirmed the polycrystalline nature of the f i l m and the fact that the c axis of the crystallite shows a preference for being normal to the surface. Photo excitation studies have indicated a further preference for the +c axis to be directed away from the substrate. A thin, semitransparent, conducting electrode was deposited on the surface of the lithium niobate and electrical properties of the resultant s m c t u e were made. Current vs voltage and capacitance vs voltage measurements were made at several frequencies. Residual changes after illumination were observed. Photo currents were also measured. 1. Fabrication and characterization of the structure. Thin films of lithium niobate approximately one micron thick have been deposited by r-f sputtering on < I 11> silicon substrates. LiNbO, powder with 10% Li,O added to compensate for Li loss was used as the target. Both n and p type silicon substrates were used. Various substrate temperature from 80' C to 600' C were used. Approximately equal partial pressures of Ar and O2 were used in the sputtering process which continued for about 8 hours in order to deposit a 1 p n thick Nm. A thin aluminum film ( peak for silicon. There are three discernable peaks from LiNb03 in this plot, i.e. <012>, <006>, and <116>. One can see that the <006> peak is 0.1 crn 2. 100 I 20 30 40 50 60 Z Q (degrees) Figure 1) X-Ray diffraction results. (a) LiNbQ, powder (AS7 card 20-631(A)) (b) 1 pn rf sputtered LiNbU, on (iii) silicon. Sample 16c. Light on \ Light o f f