Reaction of Hydrazine with Solution- and Vacuum-Prepared Selectively Terminated Si(100) Surfaces: Pathways to the Formation of Direct Si–N Bonds

Abstract

The reactivity of liquid hydrazine (N 2 H 4 ) with respect to H-, Cl-, and Br-terminated Si(100) surfaces was investigated to uncover the principles of nitrogen incorporation into the interface. This process has important implications in a wide variety of applications, including semiconductor surface passivation and functionalization, nitride growth, and many others. The use of hydrazine as a precursor allows for reactions that exclude carbon and oxygen, the primary sources of contamination in processing. In this work, the reactivity of N 2 H 4 with H-and Cl-terminated surfaces prepared by traditional solvent-based methods and with a Brterminated Si(100) prepared in ultrahigh vacuum was compared. The reactions were studied with X-ray photoelectron spectroscopy, atomic force microscopy, and scanning tunneling microscopy, and the observations were supported by computational investigations. The H-terminated surface led to the highest level of nitrogen incorporation; however, the process proceeds with increasing surface roughness, suggesting possible etching or replacement reactions. In the case of Cl-terminated (predominantly dichloride) and Br-terminated (monobromide) surfaces, the amount of nitrogen incorporation on both surfaces after the reaction with hydrazine was very similar despite the differences in preparation, initial structure, and chemical composition. Density functional theory was used to propose the possible surface structures and to analyze surface reactivity.

Solution Chemistry to Control Boron-Containing Monolayers on Silicon: Reactions of Boric Acid and 4-Fluorophenylboronic Acid with H- and Cl-terminated Si(100)

“…This investigation is summarized below in Tables 2 and 3 and targets the dihydride species for H−Si(100) and dichloride species for Cl−Si(100), which are expected to be the major species on the respective solution-prepared surfaces. 17,53,54 This computational modeling is also fully consistent with the previously described computational characterization of BCl 3 17 and N 2 H 2 30 reactions with selectively terminated Si(100) surfaces.…”

“…The Clterminated Si(100) surface also shows the intense Si 2p 3/2 feature at 99.4 eV corresponding to the silicon crystal and a very small peak at around 103 eV corresponding to the Si−O x species from the brief exposure to ambient conditions upon transfer to the XPS chamber after the monolayer formation. The formation of Si−Cl x species can be confirmed by fitting the spectra according to previous investigations within the Si 2p spectra region; 30,47 however, the Cl 2p region is more informative to confirm the reaction (Figure S3 shows a nearly complete removal of surface chlorine from the Cl−Si(100) surface in reactions with both boric acid and with 4fluorophenylboronic acid). Following the reaction of this surface with boric acid (plot b2 in Figure 2), it can be noticed that the peak at higher binding energy corresponding to SiO x species at approximately 103 eV is slightly increased and is significantly higher in intensity for the same surface reacted with 4-fluorophenylboronic acid (plot c2 in Figure 2).…”

“…Toluene was demonstrated not to react with these surfaces within the range of conditions tested, similar to previous work. 17,30 2.5. Reaction of Boric Acid with the H-and Cl−Si(100) Surfaces.…”

“…To quantify surface coverages of boron, an overlayer model was used as described in our previous work 17,30 with the following assumptions:…”

Facile collisional dissociation of N2 on a Si(111)-7x7 surface at room temperature

“…Our results could be relevant of interest in the fine comprehension of the preliminary steps of the growth of silicon nitride, which is extremely important for microelectronics. 11 The investigation of the ability of Si(111)-7x7 for an efficient synthesis of ammonia is currently investigated.…”