Stability of tetraphenyl butadiene thin films in liquid xenon

• Stability of tetraphenyl butadiene (TPB) thin films immersed in liquid xenon (LXe).
• Thermally evaporated TPB thin films were immersed in LXe for 20 h.
• Film morphology and chemical surface properties remained unchanged.
• Surface density of the films decreased by 1.6 μg/cm2 (24%) after immersion in LXe.
• For using in LXe particle detectors, TPB films should be protected with a coating.

Tetraphenyl butadiene (TPB) is widely used in particle detectors as a wavelength shifter. In this work we studied the stability of TPB thin films when immersed in liquid xenon (LXe). The thin films were deposited on glass and quartz substrates by thermal evaporation. Morphological and chemical surface properties were monitored before and after immersion into LXe by scanning electron microscopy and X-ray photoelectron spectroscopy. No appreciable changes have been detected with these two methods. Grain size and surface chemical composition were found to be identical before and after submersion into LXe. However, the film thickness, measured via optical transmission in the ultraviolet–visible wavelength regions, decreased by 1.6 μg/cm2 (24%) after immersion in LXe during 20 h. These results suggest the necessity of using a protective thin film over the Tetraphenyl butadiene when used as a wavelength shifter in LXe particle detectors.