Atomic imaging and modeling of H2O2(g) surface passivation, functionalization, and atomic layer deposition nucleation on the Ge(100) surface

Tin oxide nanostructure fabrication via sequential infiltration synthesis in block copolymer thin films

Tin oxide (SnO₂) nanostructures are attractive for sensing, catalysis, and optoelectronic applications. Here we investigate the fabrication of SnO_x nanostructures through sequential infiltration synthesis (SIS) in block copolymer (BCP) film templates. While the growth of metal and metal oxides within polymers and BCP films via SIS has been demonstrated until now using small precursors such as trimethyl aluminum and diethyl zinc, we hypothesize that SIS can be performed using larger precursors and demonstrate SnO_x SIS with tetrakis(dimethylamino)tin (TDMASn) and hydrogen peroxide. Tuning the SIS reaction and BCP chemistry resulted in highly ordered, polystyrene-block-poly(2-vinyl pyridine) (P2VP)-templated porous SnO_x - AlO_x and SnO_x nanostructures. Detailed investigation using in-situ microbalance, high resolution electron microscopy, elemental analysis and infra-red spectroscopy shows that SnO_x can directly grow within P2VP homopolymer and BCP films. Simultaneously with the growth, SnO_x SIS process also contributes to the polymer etch. Performing SnO_x SIS with pretreatment of a single AlO_x SIS cycle increases the SnO_x growth and protects the BCP template from etching. This is the first report of SnO_x SIS opening a pathway for additional tetrakis-based organometallic precursors to be utilized in growth processes within polymers.

Molecular Layer Deposition Using Ring-Opening Reactions: Molecular Modeling of the Film Growth and the Effects of Hydrogen Peroxide

Novel coating materials are constantly needed for current and future applications in the area of microelectronics, biocompatible materials, and energy-related devices. Molecular layer deposition (MLD) is answering this cry and is an increasingly important coating method for organic and hybrid organic-inorganic thin films. In this study, we have focused on hybrid inorganic-organic coatings, based on trimethylaluminum, monofunctional aromatic precursors, and ring-opening reactions with ozone. We present the MLD processes, where the films are produced with trimethylaluminum, one of the three aromatic precursors (phenol, 3-(trifluoromethyl)phenol, and 2-fluoro-4-(trifluoromethyl)benzaldehyde), ozone, and the fourth precursor, hydrogen peroxide. According to the in situ Fourier-transform infrared spectroscopy measurements, the hydrogen peroxide reacts with the surface carboxylic acid group, forming a peroxyacid structure (C(O)-O-OH), in the case of all three processes. In addition, molecular modeling for the processes with three different aromatic precursors was carried out. When combining these modeling results with the experimental research data, new interesting aspects of the film growth, reactions, and properties are exploited.

Formation of atomically ordered and chemically selective Si-O-Ti monolayer on Si0.5Ge0.5(110) for a MIS structure via H2O2(g) functionalization

Si_0.5Ge_0.5(110) surfaces were passivated and functionalized using atomic H, hydrogen peroxide (H₂O₂), and either tetrakis(dimethylamino)titanium (TDMAT) or titanium tetrachloride (TiCl₄) and studied in situ with multiple spectroscopic techniques. To passivate the dangling bonds, atomic H and H₂O₂(g) were utilized and scanning tunneling spectroscopy (STS) demonstrated unpinning of the surface Fermi level. The H₂O₂(g) could also be used to functionalize the surface for metal atomic layer deposition. After subsequent TDMAT or TiCl₄ dosing followed by a post-deposition annealing, scanning tunneling microscopy demonstrated that a thermally stable and well-ordered monolayer of TiO_x was deposited on Si_0.5Ge_0.5(110), and X-ray photoelectron spectroscopy verified that the interfaces only contained Si-O-Ti bonds and a complete absence of GeO_x. STS measurements confirmed a TiO_x monolayer without mid-gap and conduction band edge states, which should be an ideal ultrathin insulating layer in a metal-insulator-semiconductor structure. Regardless of the Ti precursors, the final Ti density and electronic structure were identical since the Ti bonding is limited by the high coordination of Ti to O.