Optical and Crystallographic Studies of Ion-Implanted Relaxor Ferroelectric Lead Zinc Niobate for Single-Crystal Layer T
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Optical and Crystallographic Studies of Ion-Implanted Relaxor Ferroelectric Lead Zinc Niobate for Single-Crystal Layer Transfer M. Levy and P. D. Moran Physics Department Michigan Technological University Houghton, MI 49931 ABSTRACT Layer separation of He+-ion implanted relaxor ferroelectric films (0.955)[Pb(Zn1/3Nb2/3)O3]– (0.045)[PbTiO3] (0.955PZN-0.045PT) has recently been reported in the literature.[1,2] Here we report on optical and X-ray diffraction analysis of the implanted material prior to separation. The formation of optical waveguides as a result of He+-ion implantation enables us to probe the sacrificial layer. A large refractive index contrast is observed between this layer and the film. Significant tetragonal distortions are also seen in the waveguide region (“the film”). Rapid thermal processing (RTP) significantly changes the peak position of the index contrast profile, possibly indicating a large redistribution of stress by He evolution in the sacrificial layer. A commensurate reduction in tetragonal distortion and local strain distribution in the waveguide region to values close to those observed before implantation is measured by triple crystal high resolution X-ray diffraction. INTRODUCTION In this work we investigate the effect of He+ ion-implantation on the sacrificial layer and film prior to crystal ion slicing in (1-x)[Pb(Zn1/3Nb2/3)O3]–(x)[PbTiO3] (PZN-PT). The crystal ion slicing process is an ion-implantation layer transfer technique described in detail before.[1,2] PZN-PT exhibits an unusually large piezoelectric response near the morphotropic phase boundary, making it quite attractive for actuator and transducer device applications.[3] The material also has an extremely large electro-optic coefficient, with r33 = 450 pm/V (λ= 632.8nm) for -poled 0.92PZN-0.08PT, and is thus of interest for use in electro-optic devices as well.[4] EXPERIMENTAL DETAIL To reproduce the ion implantation conditions described in [1] and [2], singly charged 3.8 MeV helium ions are implanted 5° off normal to the surface of bulk - oriented 0.955PZN0.045PT. -poled crystal are used. The implant dose and temperature are 5x1016 ions/cm2 and at 58°C, respectively. The optical and structural properties of the implanted samples are characterized before and after a 40s RTP in forming gas (5% H, 95% N) at 550 °C. [1,2] Characterization of the waveguides is performed by prism coupling at He-Ne wavelength 632.8nm. A rutile prism cut at 60° is used in the prism coupler. High resolution x-ray diffraction analysis is performed using CuKα1 radiation (λ=1.54056A) incident upon the sample
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mounted in a triple crystal diffractometer. The sample is oriented so as to diffract from the PZNPT (002) planes. RESULTS AND DISCUSSION Prism-coupled data plotted in Fig.1 for transverse electric (TE) modes show that the waveguide characteristics are different before (Fig. 1a) and after (Fig. 1b) RTP. In these data the reflected optical intensity is measured as a function of incident angle onto the waveguide structure. The moda
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