Surface Chemical Analysis Using Multiply Charged Ions

Abstract

A secondary-ion mass spectroscopic study of a wurtzite GaN(0001) surface was conducted to test the operation of a novel surface-chemical analyzer using Ar 3+ (7.5 keV) and Ar 4+ (10 keV) ions. The analyzer allows us to measure the time of flight of a secondary ion simultaneously with the detection of the backscattered atom or ion that captured electrons from the surface atoms. A proton, CmH + n (m = 1-6 and n = 0-13), N + , Ga + , and GaN + ions were observed in the mass spectrum. The spectral width and profile were different between Ar 0 and Ar + -coincidence measurements.

Coincidence measurements of secondary ions and scattered ions in collision between slow Ar6+and a GaN(0001) surface

“…The details of the experimental apparatus were described elsewhere [7], so a brief description is presented here. Figure 1 shows a schematic illustration of the experimental setup.…”

“…Figure 5(b) is almost the same as the usual SIMS spectrum, since T 1 is much longer than T 2 . Very efficient proton emission is one of the most important characteristics of desorption and ionization due to electron capture by HCIs [1,[4][5][6][7]. Weak N + , Ga + and GaN + peaks originating from substrate atoms were also observed, together with some hydrocarbon-ion peaks originating from contaminants.…”

“…A novel experimental apparatus allowing us to achieve multi-coincidence measurements among scattered atoms/ions, secondary electrons and secondary ions has been developed to clarify the sputtering or desorption processes due to electronic excitation induced by slow HCIs [4][5][6][7]. This paper will report the first experimental SIMS results measured in coincidence with scattered ions whose charge state and kinetic energy were selected in collisions between HCIs and the solid surfaces.…”

Selective Sputtering of Impurity Hydrogen Atoms from a GaN(0001) Surface by Slow Multicharged Ion Impact

“…The potential sputtering (PS) induced by slow multicharged ion impacts is increasingly attracting attention from this point of view, 5) because of its two features of sitespecific desorption and slight damage to the bulk. [6][7][8][9][10][11][12] The author succeeded in direct observation of PS of protons on the GaN surfaces irradiated with Ar 6þ by a coincidence measurement of scattered Ar þ ions. 7,9) However, the observed PS was not the dominant process because the number of scattered Ar þ ions was only 23% of that of all scattered Ar atoms/ions.…”

“…The detailed experimental setup and procedure in this study are described elsewhere, [6][7][8] and are mentioned only briefly in this paper. Ar qþ ions with charge state q (4, 6, or 8) and kinetic energy E 0 (2:5 Â q keV) were irradiated tangentially onto a GaN(0001) (Ga face) surface at an angle of $10 with respect to the surface.…”