Na0.5K0.5NbO3/SiO2/Si thin film varactor

Perfectly c-axis oriented micrometer thick Na0.5K0.5NbO3(NKN) films have be en prepared on a thermally grown ultrathin SiO2 template layer onto a Si(00 1) wafer by the pulsed laser deposition technique. A x-ray diffraction thet a-2 theta scan reveals multiple-cell structuring of single phase NKN film a long the polar axis, while films grown onto amorphous ceramic (Corning) gla ss show a mixture of slightly c-axis oriented NKN and pyrochlore phases. Th is implies a small amount of SiO2 crystallites distributed in an amorphous matrix inherit Si(001) orientation and promotes highly oriented NKN film gr owth. NKN film dielectric permittivity epsilon' was found to vary from 114. 0 to 107.2 in the frequency range 1 kHz-1 MHz, while the resistivity was on the order of 2.6 x 10(10) Ohm cm @ 20 kV/cm. The planar interdigital varia ble reactance device (varactor) based on the NKN/SiO2/Si thin film structur e possesses a dissipation factor of 0.8% at 1 MHz and zero bias, electrical tunability of 3.1%, and nA order leakage current at 20 V bias at room temp erature. (C) 2000 American Institute of Physics. [S0003-6951(00)04813-0].