What is it about?

(1) We critically evaluated methods reported in the literature using comprehensive surface analysis techniques including atomic force microscopy, XPS and contact angle measurements. (2) We found that reported methods did not perform well in terms of removing both organic and particulate contaminants from the (0 0 0 1) basal surface. (3) We proposed a new wet-cleaning method showing outstanding cleaning performance based on modified RCA cleaning protocols after thoroughly examining the cleaning effect of various chemical solutions and UV light and plasma irradiation.

Featured Image

Why is it important?

(1) A reliable wet-cleaning method for sapphire showing outstanding cleaning performance is firmly established. (2) Validity of reported wet/dry cleaning methods are critically evaluated. (3) This new reliable method will be very useful for the device applications and next-step surface chemistry study of single-crystal a-Al2O3. (4) AFM should be wisely used as an indispensable tool for surface contamination control studies, owing to its high spatial resolution and sensitivity as a local probe technique.


(1) Sapphire are extremely challenging substrates for critical cleaning because of its chemical inertness and susceptibility to foreign contaminants (likely due to higher iso-electric point than glass/silica)! (2) Conventional recipes valid for easy-to-handle substrates like silica/glass are basically invalid for sapphire. Be cautious in the traditional wisdom. (3) This work is the outcome of Ms. Dan Zhang's two years hard work. The paper was awarded the highly competitive first Franz Habraken Best Paper Award (2014) of Applied Surface Science (Elsevier).

Professor Yang Gan
Harbin Institute of Technology

Read the Original

This page is a summary of: Characterization of critically cleaned sapphire single-crystal substrates by atomic force microscopy, XPS and contact angle measurements, Applied Surface Science, June 2013, Elsevier, DOI: 10.1016/j.apsusc.2012.12.143.
You can read the full text:




The following have contributed to this page