Hydrogen depth profiles

An especially significant application of NRA is the measurement of quantified hydrogen depth profiles, which is difficult using all but a few other analytical techniques. Hydrogen concentrations can be measured to a few tens or hundreds of parts per million (ppm) and with depth resolutions on the order of 10 nm. 

Fig. 5. Hydrogen depth profile of a deuterated polystyrene PS(D) film deposited on a protonated polystyrene PS(H) film on top of a silicon wafer as obtained by l5N-nuclear reaction analysis ( 5N-NRA). The small hydrogen peak at the surface is due to contamination (probably water) of the surface. The sharp interface between PS(D) and PS(H) is smeared by the experimental resolution (approx. 10 nm at a depth of 80 nm) [57], The solid line is a guide for the eye...

Fig. 6. Hydrogen depth profile of a thin film of poly(p-methylstyrene)(H)/ PS(D) diblock copolymer, PMS(H)-b-PS(D), on a silicon wafer as obtained by the l5N-NRA technique [57]. The sample has been annealed for 1 h at 140 °C. PMS(H) is largely enriched at the surface. The solid line is a guide to the eye...

Fig. 2 Schematic diagram of a hydrogen depth profiling setup using a high efficiency BGO detector. A cooled sample holder is placed close to the front surface of the BGO scintillator in ultra-high vacuum. The sample holder can be moved perpendicular to the plane of the figure to bring different samples into the 15N beam and is surrounded by a Faraday cup arrangement to ensure accurate measurement of the analyzing beam dose.

Fig. 10. Hydrogen depth profiles obtained from the resonant nuclear reaction of an as-deposited a-Si H film and after laser annealing at different intensities. [After Thomas et al.

Figure 8. Hydrogen depth profile in Kapton (a) from a composite spectrum taken at different spots and (b) from a spectrum at one spot.

Petit J. C., Della Mea G., Dran J.-C., and Schott J. (1987) Mechanism of diopside dissolution from hydrogen depth profiling. Nature 32S, 705-707. 

In agreement with hydrogen depth profiling and XPS analyses, these results show that the basalt glass surface is depleted in network modifying cations that... 

First, hydrogen-depth profiling performed on reacted aluminosilicates shows that the preferential removal of some metals proceeds via an exchange reaction with H + or H30 + /H20 (i.e. compare Na and H profiles reported in Fig. 12). As a result, silicate surfaces become protonated and/or hydrated to depths of several hundred angstroms or more depending on pH and temperature (Fig. 12). 

Figure 18 Hydrogen depth profile measured with SNMS in an amorphous hydrogenated Si layer with a P-doped n-layer on top. Curve theoretical depicts the H-profile expected from the partial pressure variations during the sputter deposition process.

Mostly light particles are used protons, deuterons, and He ions (A heavier ion, N, is applied to special analyses - hydrogen depth profiling — at around 7 MeV.)... 

Fig. 6. Hydrogen depth profiles of Pd (5 nm) capped YHjc (500 nm) films with (a) x = 2.86 and (b) x 1.9, determined by method. Vertical dotted lines represent the apparent thickness of the films (Huiberts et al., 1996b).

For hydrogen depth profiling in polymers, He is the most commonly used incident ion. ERDA experiments are somewhat more challenging for the novice user than are backscattering experiments, as the incident beam is also scattered toward the detector with comparable energy to the forward scattered hydrogen nuclei that are of interest. There are usually some orders of... 

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