Takayuki Kawamoto

Effects of sputtering gas conditions on formation of (1120) textured ZnO films

The ZnO films in which the crystallite c-axis is unidirectionally aligned in the substrate plane [(110) textured ZnO films] enable the realization of shear mode devices in the ultra high frequency (UHF) range. In this study, we have investigated the (110) textured ZnO film, focusing on the effect of total gas pressure and partial gas pressure of oxygen and argon during sputtering deposition. The crystallographic characteristics of the films were measured by X-ray diffraction (XRD) analysis. In addition, optical emissions from the RF plasma were analyzed to investigate the effect of ionic species on the growth of the ZnO films. Highly crystallized (110) textured ZnO films were obtained under the conditions of low total gas pressure and high oxygen gas concentration. Under these conditions, strong optical emission spectra from oxygen species were observed. From these results, we conclude that energetic oxygen particle bombardment to the substrate contributes to the (110) texture formation. The film with an ω-scan rocking curve FWHM of 3.3° showed a k15 value of 0.16, which was 62% of the value for a single crystal.

Large-Area Growth of In-Plane Oriented (1120) ZnO Films by Linear Cathode Magnetron Sputtering

(1120) textured ZnO films are good candidates for shear-mode piezoelectric devices. In the previous deposition techniques of these films, there have been two problems related to their practical application. These problems are as follows: (i) highly oriented films can be obtained only in a small area and (ii) the crystallite c-axis of in the films is radially oriented in the substrate plane. To resolve these problems, the sputtering deposition technique using a linear cathode has been proposed. The in-plane and out-of-plane orientations of the films were quantitatively determined by pole figure analysis. As a result, we have demonstrated the formation of in-plane unidirectionally oriented (1120) ZnO films over the entire area of 4-in. silicon wafers.

Observation of Induced Shear Acoustic Phonons by Brillouin Scattering

As the first step in realizing the simple and nondestructive measurement of shear waves in the GHz range, a technique involving Brillouin scattering and a ZnO shear wave transducer is proposed. Making use of transmitted shear waves, we have succeeded in observing a strong Stokes Brillouin peak in the quartz sample. This technique can be applied to the measurement of anisotropic layers and small samples.

P1M-4 Study on Formation Mechanism of (1120) Textured ZnO Films

The ZnO films where crystallites c-axis are unidirectionally aligned in the substrate plane ((112macr0) textured ZnO films) realize shear mode devices. In this study, we have studied the formation mechanism of the (112macr0) textured ZnO film, focusing on the effect of total pressure and partial pressure of oxygen and argon during sputtering deposition. In addition to the X-ray diffraction (XRD) measurement of the films, optical emissions from the RF plasma were analyzed to investigate the effect of ionic species on the growth of the ZnO films. Highly crystallized (112macr0) textured ZnO films were obtained in conditions of low total gas pressure and high oxygen concentration. In these conditions, strong optical emission spectra from oxygen species were strongly observed. The best shear mode electromechanical coupling coefficient k15 of the film was 0.16, which was 62 % of the value of single crystal