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DOE OSTI2021

Chemistry of Titanium Deposition Precursors for Area-Selective Deposition of Functionalized Silicon [Posters]

Area-selective atomic layer deposition (AS-ALD) is an appealing bottom-up fabrication technique that can produce atomic-scale device features, overcoming challenges in current industrial techniques such as edge alignment errors. TiCI 4 is a common thermal ALD precursor for Ti0 2 thin films, which are appealing candidates for DRAM capacitors due to their excellent dielectric constants. Hydrogen and chlorine termination passivate the Si surface, allowing for selective deposition of TiCI 4 onto HO-terminated areas. However, selectivity loss occurs after several ALD cycles. Ti oxide nucleates onto surface defects on Cl- and H-Si resists. Previously, the use of H-Si as an ALD resist has been studied extensively, but less work has focused on chemical forces driving nucleation, especially for Cl-Si. Here, formation of defect nuclei was investigated with selectivity loss during Ti0 2 ALD with TiCI 4 and water on the (100) and (111) crystal surfaces of hydrogenated, chlorinated, and oxidized Si.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2026

Syngas Production at Si Hybrid Photoelectrodes Modified with Re(I) and Mn(I) Tricarbonyl Phenanthroline Complexes Containing Reactive Aryl Azide Groups

We installed molecular CO 2 reduction (CO 2 R) catalysts directly onto Si (photo)electrodes. The highly reactive M(5-azido-1,10-phenanthroline)(CO) 3 X (where M = Mn or Re, X = Br or Cl) complexes readily bubbled when dissolved in polar organic solvents, in both the presence and absence of an ultraviolet light source. When placed on hydrogen-terminated Si (H-Si) and native silicon oxide (SiOx), similar amounts of the complex were attached to the surface under illumination (367 nm, 50–200 mW/cm 2 ) or in the dark. Surprisingly, these films revealed submonolayer coverages instead of the multilayered structures we expected. DFT analyses support monolayer formation, showing that the triplet-state nitrene of the complex is more energetically favorable than the singlet state. Using controlled-potential electrolysis experiments, we showed that Re- and Mn-containing films on pSi photoelectrodes generated small amounts of CO when exposed to 1 atm of CO 2 and 1 sun illumination. These amounts of CO were an order of magnitude greater than control surfaces, producing 5.59 × 10 –7 mol CO/h for Re(az-phen) and 7.83 × 10 –7 mol CO/h for Mn(az-phen) films. Much of the charge passed at the pSi electrodes was consumed by the competing hydrogen evolution reaction, which we attribute to the low molecular coverage and the presence of native oxide on the electrode surface after attachment. Finally, this work demonstrates the feasibility of reacting azide-containing ligands with Si surfaces. Still, it highlights the need for alternative ligand structures and reaction conditions to form multilayer films.

azides↗

DOE OSTI2020

Materials Data on SiH4 by Materials Project

SiH4 is Silicon tetrafluoride-like structured and crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four silane molecules. Si4- is bonded in a tetrahedral geometry to four H1+ atoms. All Si–H bond lengths are 1.49 Å. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one Si4- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one Si4- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one Si4- atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on SiH by Materials Project

SiH is Cubane-like structured and crystallizes in the trigonal P-3m1 space group. The structure is zero-dimensional and consists of two silylidyne molecules. Si is bonded in a single-bond geometry to one H atom. The Si–H bond length is 1.50 Å. H is bonded in a single-bond geometry to one Si atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on SiH8 by Materials Project

SiH4(H2)2 is Silicon tetrafluoride-like structured and crystallizes in the tetragonal I-4m2 space group. The structure is zero-dimensional and consists of four hydrogen molecules and two silane molecules.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Si3H by Materials Project

(Si)6H2 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional and consists of four hydrogen molecules and one Si framework. In the Si framework, there are two inequivalent Si sites. In the first Si site, Si is bonded to four equivalent Si atoms to form a mixture of distorted edge and corner-sharing SiSi4 tetrahedra. All Si–Si bond lengths are 2.51 Å. In the second Si site, Si is bonded in a body-centered cubic geometry to eight equivalent Si atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Si3H by Materials Project

Si3H crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of three Si3H sheets oriented in the (0, 0, 1) direction. there are three inequivalent Si sites. In the first Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are three shorter (2.36 Å) and one longer (2.39 Å) Si–Si bond lengths. In the second Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. All Si–Si bond lengths are 2.37 Å. In the third Si site, Si is bonded in a single-bond geometry to three equivalent Si and one H atom. The Si–H bond length is 1.50 Å. H is bonded in a single-bond geometry to one Si atom.

36 MATERIALS SCIENCE↗