Spontaneous N Incorporation onto a Si(100) Surface

Abstract

Initial nitridation of the Si(100) surface is investigated using photoemission, ion-scattering and ab initio calculations. After dissociation of NO or NH3, nitrogen atoms are found to spontaneously form a stable, highly coordinated N[triple bond]Si(3) species even at room temperature. The majority of the N species is incorporated into the subsurface Si layers occupying an interstitial site, whose atomic structure and unique bonding mechanism is clarified through ab initio calculations. This unusual adsorption behavior elucidates the atomistic mechanism of initial silicon nitride formation on the surface and has important implication on the N-rich layer formation at the SiO(x)N(y)/Si interface.

Thermal decomposition of NH3 on the Si(100) surface

“…N1 and N2 peaks may straightforwardly be assigned as due to the N atoms without any N-H bond (Si 3 BN) and those with one N-H bond (Si 2 @NH), respectively, in comparison to N3 for Si-NH 2 . In fact, the previous experiments agree well on the binding energy of the fully dissociated N species for NO or NH 3 adsorption on Si(1 0 0) as being identical to that of N1 [21,23]. A similar N 1s binding energy is also reported for the Si 3 BN species at the Si-rich interface of SiON/Si(001) [24].…”

“…Although such a subsurface incorporation successfully explain the depth distribution observed here, a minor occupation of the shallower sites S or I cannot be excluded. In addition, one should be careful in a direct comparison of the earlier theoretical results suggesting the I or S [6,25] with our recent one [21] because the previous ones assumed all surface Si dangling bonds are saturated by H atoms in contrast to our assumption of no H adsorbates [21]. Based on this difference, it may be argued that the ''deep'' subsurface incorporation occurs only at a temperature high enough to desorb H atoms.…”

“…While a recent calculation suggested the I site [inserted between the first and the second Si layers, see Fig. 1(d)] as the most stable one [6], we very recently showed, through photoemission and ion-scattering experiments and also first-principles calculations, that the fully dissociated N species is spontaneously incorporated into the subsurface layers, most stably near the third Si layer [21]. Although such a subsurface incorporation successfully explain the depth distribution observed here, a minor occupation of the shallower sites S or I cannot be excluded.…”

“…A few other studies using ion scattering spectroscopy suggested that the dissociated N atoms diffuse into the Si subsurface layers after high-temperature annealing [3,12]. Very recently, our group successfully characterized the atomic structure of such subsurface N species after full dissociation [21].…”

Quantitative XPS analysis of hydrosilated 1-alkene and 1-alkyne at terraced, dihydrogen-terminated, 1 × 1 (100) silicon

“…(It is worth noting that in a recent study of room-temperature silicon nitridation by NO and NH 3 , Kim et al have reported that nitrogen accumulates in a subsurface region. 40 ) On freshly prepared grafted surfaces the oxygen amount was found to be of the order of two monolayers. The O 1s/C 1s and Si 2p/O 1s intensity ratios, both increasing with Â, show that such an oxygen is localized at the interface between the silicon surface and the carbonaceous layer.…”