Rate equations for collision-induced desorption and abstraction in the reaction system H(g)+D/Si(100)→D2,HD at 573 K

Abstract

Abstraction and desorption kinetics in the reaction of H + D/Si (100) and the relation to surface structure Abstraction of chemisorbed bromine from the Si(111) surface by incident hydrogen atoms Collision-induced desorption ͑CID͒ and Eley-Rideal ͑ER͒ type abstraction have been investigated in the reaction system, H(g)ϩD ad /Si͑100͒→D 2 ,HD, at surface temperature of 573 K where dihydride phase is unstable. Rate equations for CID were obtained based on a second-order kinetics with respect to doubly occupied Si dimers DSi-SiD, DSi-SiH, and HSi-SiH, which are considered as parent species of transiently formed dihydrides, DSiD, DSiH, and HSiH, respectively. The coverages of the doubly occupied dimers were determined as a function of H exposure time by means of temperature-programmed-desorption ͑TPD͒, and then the rate equations were calculated. As a result, the experimental D 2 and HD rate curves were reasonably fit with the rate equations formulated. This fact indicates that CID is induced when two dihydride species encounter during their propagation via dihydride-monohydride isomerization reactions. It was found that HSi-SiH does not play a role in CID of both D 2 and HD. Possible origins of this isotope effect were discussed in terms of quantum effects on associative desorption and diffusion processes. The HD rate curve due to direct ER abstraction channel was fit with a first-order kinetics in D ad coverage for a low coverage regime where dangling bonds exist. However, for a high coverage regime where the surface is saturated, the HD rate curve was fit with DSi-SiD coverages, suggesting that D ad that are paired up with H ad in the same Si dimers are not abstracted.

Hot-complex-mediated abstraction and desorption of D adatoms by H on Si(100)

“…Besides, taking into account the feature that the ABS rate curve is a simply decreasing function with decreasing D on the saturated surface, the maximum in the HD rate around D ϭ0.85 ML is attributed to HD CID overlapping ABS. With the light of the present results and the rate-curve analysis done at T s ϭ573 K, 14 we confirm that Eq. ͑1͒ and the physics and chemistry behind it are valid.…”

“…Actually, the observed HD rate curves exhibit a bimodal structure particularly at small initial D coverages D 0 , suggesting the occurrence of two distinct channels, i.e., HD CID along the LH mechanism and ABS via the direct ER mechanism. 7 Khanom et al 14 propose a HD rate equation to fit to the experimental data obtained for D 0 ϭ1.0 ML ͑ML: monolayer, one D atom per surface Si atom͒, dN HD dt ϭk ABS DD ϩC 1 HD DD ϩ2C 2 HD HD ϩC 3 HD HH ,…”

Rate equation analysis of hydrogen uptake on Si (100) surfaces

“…This is because possible isotope effects are included in the ABS and AID processes when lighter atoms are preferentially abstracted in such a H and D coadsorption system. 18,43 Figure 5 shows the plots of the initial HD and D 2 rates measured as a function of T s . The measured AID rate curve for the D 2 desorption has a peak in the temperature region 470 K ഛ T s ഛ 600 K. The observed peak of the AID rate curve is much broader than the peak previously observed on the nonsaturated 1.0 ML D / Si ͑100͒ surface.…”

“…So far, the abstraction reactions have been studied mainly from a kinetics point of view [9][10][11][12][13][14][15][16][17][18][19][20][21][22] rather than from a dynamics point of view. [23][24][25][26][27] Dinger, Lutterloh, and Küppers 9,20 reported that the reactions of Eqs.…”

Modulated hydrogen beam study of adsorption-induced desorption of deuterium from Si(100)-3×1:D surfaces

“…This hydrogen abstraction ͑ABS͒ by gas phase H atoms is of great technological relevance to electronic device processes such as plasma-enhanced chemical vapor deposition of thin Si films. 1 So far, the kinetic mechanism of the hydrogen abstraction reactions has been extensively studied by isotopic labeling of adatoms in the system HϩD/Si from an uptake [2][3][4][5][6][7][8][9] as well as from a desorption [10][11][12][13][14][15][16][17][18][19] point of view. It has been well established that the abstraction reactions observed in the desorption experiments 13,14,18,19 can be categorized either into a direct abstraction ͑ABS͒ of adatoms by gas phase atoms to form HD molecules, ABS: HϩD/Si→HD, or into an indirect abstraction or adsorption-induced desorption ͑AID͒ of surface adatoms to form D 2 molecules, AID: HϩD/Si→D 2 .…”