Glass - Back to the Future!

Presenting Author:
Ray-Jay Jeng

article posted 5 April 2016

Ray-Jay Jeng received his Master of Science degree from the Department of Material Science and Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan. Currently, he is a PhD graduate student oriented by Professor Tetsuji Yano in the Department of Chemistry and Material Science, Tokyo Institute of Technology, Tokyo, Japan.

Direct bonding of tellurite glass film on substrate materials at room temperature

Ray-Jay Jeng*, Tetsuo Kishi, Tetsuji Yano
Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku,
Tokyo 152-8550, Japan

Tellurite glass is well known as a high functional glass material for the optical device because of its ultra-high optical transparency, high-nonlinear refractive index, and high-chemical durability. Formation of layered structure of thin tellurite-glass film on substrate is important to fabricate the optical circuit. In order to reduce the birefringence due to the difference of the thermal expansion coefficient between glass and substrate, the formation of film on the substrate at room temperature would be much better. Direct bonding technique is considered to be one of the key processes to realize the formation of thin glass film on the substrate at ambient temperature. However, it has been focused mainly in the field of the silicon wafer processing. In this study, thin film formation of tellurite glass on the optical substrate materials using the direct bonding technique is investigated to realize optical circuit using tellurite glass system for the photon propagating media.
10B2O3135Nb2O5765TeO2 glass (in mol%) is chosen for the film composition. Its Tg and CTE (coefficient of thermal expansion) are 386C and 11610-7 K-1, respectively. Thin tellurite glass film is formed by the glassblowing technique. By the optimization of the blowing condition, thin tellurite-glass film with 2-4 m thickness can be prepared. The film is placed on the substrate and pressed at 980012000 Pa for 23 s at room temperature in air. For example, Figure 1 shows an SEM image of the cross section of the film on the glass substrate (CTE=8710-7 K-1). Very smooth contact of the film with the glass substrate is clearly observed, and the direct bond of the tellurite glass film with various substrate materials are evaluated, and the mechanism of the direct bonding of the tellurite glass with substrate materials is discussed from the point of view of chemical bond formation.

Figure 1. The SEM cross sectional image of the coated sample. The tellurite glass film was coated on a slide glass as the substrate at the bottom. The thickness of the tellurite glass film is 219008 m