Properties of GaP(001) Surfaces Treated in Aqueous NH4F Solution

Abstract

Properties of GaP(001) surfaces treated in a saturated solution have been investigated using spectroscopic ellipsometry (SE), ex situ atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and wettability measurements. The SE data clearly indicate that the aqueous solution causes thinning of the native GaP oxide upon immersing the sample in the solution for . Further immersion leads to surface roughening, as confirmed by the SE and AFM observation. The AFM root-mean-square values obtained are , , and for (as-degreased), four days, and one week, respectively. The XPS spectra support the thinning of the native GaP oxide by the etching. The SE and XPS spectra, however, suggest that the native oxide film cannot be completely etch removed by the treatment. One reason for this may be due to the fact that as soon as the etched surface is exposed to air, the oxidation starts to occur. The wettability measurements indicate that the as-degreased surface is hydrophobic, while the -treated surface is hydrophilic.