1. Cryogenic Si-Si Bond Strength Testing
2nd ET Annual Workshop October 2009
Cryogenic Si-Si Bond Strength Testing
Nicola Beveridge1, Mariëlle van Veggel1, Jim Hough1, Sheila Rowan1, Ronny Nawrodt1, Stuart Reid1, Bostjan Besentzek1, John Davidson2, Donald Nicholson3
1 Institute for Gravitational Research, University of Glasgow
2 Faculty of Mechanical Engineering, University of Glasgow
3 Faculty of Electrical Engineering, University of Glasgow 1

2. Research Aims
Assess suitability of silicate bonding for use in 3rd generation detectors
Strength of silicon-silicon silicate bonds at cryogenic temperature
Previous research has shown silicate bonded silicon to be as strong as silicate bonded silica in room temperature shear strength tests
Strength testing at room temperature then at cryogenic temperature, using liquid nitrogen as a coolant.
RTT results and CTT results should give an indication of the effect of cooling the bonds.
Initial focus on wet nitrogen oxidation: oxidation layer needed to prevent hydrogen gas being produced (which will weaken/damage bond) when silicon comes in contact with bonding solution
Previous research shown spikes are present after oxidation in a dry oxidation environment
The sample holder was placed in an insulated PTFE bath, and liquid nitrogen added until the samples and bottom part of the loading arm were submerged and at temperature.
Zwick-Rowell 2.0 machine 2

3. Results 28 Room Temperature Tests (R01 – R28)
29 Cryogenic Temperature Tests (C01 – C29)
2 Cryogenic unusable results due to the machine malfunctioning during testing
Two types of break – slightly weaker bond breaks, and slightly stronger diagonal breaks. 3

4. Average silica-silica bond strength
Results
Average silica-silica bond strength
Red line indicates average strength for silica-silica room temperature strength tests
No significant difference between cryogenic strengths and room temp strengths. Similar average, higher range and standard deviation
No correlation between the minimum oxide layer of the sample and strength – no strength advantage to a thicker oxide layer.
To date no correlation seen between oxide thickness and strength 4

5. Results 5

6. Conclusions
Average strength of silicate bonds between samples of oxidised silicon higher than silicate bonds between pieces of silica
Strength of bond is not significantly changed by cooling to cryogenic temperatures
Conclusion from initial research
This suggests silicon is a good candidate as a construction material for the suspension system in 3rd generation detectors systems. 6

7. Future Work Add control samples Identify minimum oxide layer thickness
Shear and tensile strength tests
Dry oxidation technique
Establish minimum oxide layer required for a successful bond with wet nitrogen technique.
Perform shear and tensile tests
Prepare samples using dry oxidation technique and compare results
Thermal conductivity of silicon-silicon hydroxide bonds
Bond mechanical loss measurements 7