Effect of crystalline quality of diamond film to the propagation loss of surface acoustic wave devices

Abstract

Diamond films with various crystal qualities were grown by chemical vapor deposition on silicon wafers. Their crystallinity was characterized by Raman scattering and electron backscattering diffraction. By fabricating a device structure for surface acoustic wave (SAW) using these diamond films, the propagation loss was measured at 1.8 GHz and compared with the crystallinity. It was found that the propagation loss was lowered in relatively degraded films having small crystallites, a narrow distribution in the diamond crystallite size, and preferential grain orientation. This experiment clarifies diamond film characteristics required for high-frequency applications in SAW filters.

High‐frequency surface acoustic wave filter based on diamond thin film

“…From the results of Raman scattering and EBSD measurements, we found that there was less propagation loss of the SAW in a relatively degraded‐crystalline‐quality diamond thin film with small grains, a narrow distribution of grains, and preferential grain orientation. These results suggest that the dependence of phase velocities on crystal directions is reduced and that the effect of the grain boundaries is minimized 9, 10.…”

“… (online color at: http://www.pss-a.com/) Image quality map obtained by analyzing EBSD measurements. A–C correspond to the values listed in Table 1 9. …”

A 3D tomographic EBSD analysis of a CVD diamond thin film

“…For optical applications, the properties of (001)-oriented diamond films are superior to those of (111)-oriented films in terms of the refractive index and extinction coefficient [11]. Beyond these basic texture-property relations [17], more specific studies on the relationship between texture and microstructure have been reported for diamond [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31].…”

“…Although important texture results for diamond have been obtained by x-ray diffraction (XRD), electron backscatter diffraction (EBSD) provides more detailed information about the texture, grain size, and interfaces of such films [18][19][20][21][22]26]. For instance, an important contribution in this area was made by Fujii et al [23]. In their work, the authors quantified the crystallinity, texture, and crystal size of diamond films by Raman scattering and EBSD, and they subsequently correlated the data with the propagation loss of surface acoustic waves measured at 1.8 GHz.…”

Structural, electrical and piezoelectric properties of LiNbO3 thin films for surface acoustic wave resonators applications

“….) [4][5][6]. Among those materials having interesting electro-optic and piezoelectric coefficients, lithium niobate (LiNbO 3 ) is a good candidate for coupling with NCD substrates.…”