A Rare Low Spin Co(IV) Bis-Silyldiamide with High Thermal Stability: Exploring the Origin of an Unusual S = 1/2 Configuration

2020 ◽  
Author(s):  
David Zanders ◽  
Goran Bačić ◽  
Dominique Leckie ◽  
Oluwadamilola Odegbesan ◽  
Jeremy M. Rawson ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Density Functional ◽  
Atomic Layer ◽  
Epr Spectrum ◽  
Functional Theory ◽  
Cluster Calculations ◽  
Layer Deposition ◽  
Starting Point ◽  
Higher Spin ◽  
Surface Saturation

Attempted preparation of a chelated Co(II) β-silylamide re-sulted in the unprecedented disproportionation to Co(0) and a spirocyclic cobalt(IV) bis(β-silyldiamide): [Co[(NtBu)2SiMe2]2] (1). Compound 1 exhibits a room temperature magnetic moment of 1.8 B.M and a solid state axial EPR spectrum diagnostic of a rare S = 1/2 configuration. Semicanonical coupled-cluster calculations (DLPNO-CCSD(T)) revealed the doublet state was clearly preferred (–27 kcal/mol) over higher spin configurations for which density functional theory (DFT) showed no energetic preference. Unlike other Co(IV) complexes, 1 had remarkable thermal stability, and was demonstrated to form a stable self-limiting monolayer in initial atomic layer deposition (ALD) surface saturation tests. The ease of synthesis and high-stability make 1 an attractive starting point to begin investigating otherwise inaccessible Co(IV) intermediates and synthesizing new materials.

scholarly journals A Rare Low Spin Co(IV) Bis-Silyldiamide with High Thermal Stability: Exploring the Origin of an Unusual S = 1/2 Configuration

2020 ◽  
Author(s):  
David Zanders ◽  
Goran Bačić ◽  
Dominique Leckie ◽  
Oluwadamilola Odegbesan ◽  
Jeremy M. Rawson ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Density Functional ◽  
Atomic Layer ◽  
Epr Spectrum ◽  
Functional Theory ◽  
Cluster Calculations ◽  
Layer Deposition ◽  
Starting Point ◽  
Higher Spin ◽  
Surface Saturation

Attempted preparation of a chelated Co(II) β-silylamide re-sulted in the unprecedented disproportionation to Co(0) and a spirocyclic cobalt(IV) bis(β-silyldiamide): [Co[(NtBu)2SiMe2]2] (1). Compound 1 exhibits a room temperature magnetic moment of 1.8 B.M and a solid state axial EPR spectrum diagnostic of a rare S = 1/2 configuration. Semicanonical coupled-cluster calculations (DLPNO-CCSD(T)) revealed the doublet state was clearly preferred (–27 kcal/mol) over higher spin configurations for which density functional theory (DFT) showed no energetic preference. Unlike other Co(IV) complexes, 1 had remarkable thermal stability, and was demonstrated to form a stable self-limiting monolayer in initial atomic layer deposition (ALD) surface saturation tests. The ease of synthesis and high-stability make 1 an attractive starting point to begin investigating otherwise inaccessible Co(IV) intermediates and synthesizing new materials.

A Rare Low Spin Co(IV) Bis-Silyldiamide with High Thermal Stability: Exploring the Origin of an Unusual S = 1/2 Configuration

2020 ◽  
Author(s):  
David Zanders ◽  
Goran Bačić ◽  
Dominique Leckie ◽  
Oluwadamilola Odegbesan ◽  
Jeremy M. Rawson ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Density Functional ◽  
Atomic Layer ◽  
Epr Spectrum ◽  
Functional Theory ◽  
Cluster Calculations ◽  
Layer Deposition ◽  
Starting Point ◽  
Higher Spin ◽  
Surface Saturation

Attempted preparation of a chelated Co(II) β-silylamide re-sulted in the unprecedented disproportionation to Co(0) and a spirocyclic cobalt(IV) bis(β-silyldiamide): [Co[(NtBu)2SiMe2]2] (1). Compound 1 exhibits a room temperature magnetic moment of 1.8 B.M and a solid state axial EPR spectrum diagnostic of a rare S = 1/2 configuration. Semicanonical coupled-cluster calculations (DLPNO-CCSD(T)) revealed the doublet state was clearly preferred (–27 kcal/mol) over higher spin configurations for which density functional theory (DFT) showed no energetic preference. Unlike other Co(IV) complexes, 1 had remarkable thermal stability, and was demonstrated to form a stable self-limiting monolayer in initial atomic layer deposition (ALD) surface saturation tests. The ease of synthesis and high-stability make 1 an attractive starting point to begin investigating otherwise inaccessible Co(IV) intermediates and synthesizing new materials.

scholarly journals Sn-Doped Hematite for Photoelectrochemical Water Splitting: The Effect of Sn Concentration

2020 ◽  
Vol 234 (4) ◽  
pp. 683-698 ◽  
Author(s):  
Siyuan Zhang ◽  
Hamidreza Hajiyani ◽  
Alexander G. Hufnagel ◽  
Jonathan Kampmann ◽  
Benjamin Breitbach ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Atomic Layer ◽  
Solubility Limit ◽  
Metallic State ◽  
Equilibrium Solubility ◽  
Functional Theory ◽  
Sn Doping ◽  
Layer Deposition

AbstractHematite-based photoanodes have been intensively studied for photoelectrochemical water oxidation. The n-type dopant Sn has been shown to benefit the activity of hematite anodes. We demonstrate in this study that Sn-doped hematite thin films grown by atomic layer deposition can achieve uniform doping across the film thickness up to at least 32 mol%, far exceeding the equilibrium solubility limit of less than 1 mol%. On the other hand, with the introduction of Sn doping, the hematite crystallite size decreases and many twin boundaries form in the film, which may contribute to the low photocurrent observed in these films. Density functional theory calculations with a Hubbard U term show that Sn doping has multiple effects on the hematite properties. With increasing Sn4+ content, the Fe2+ concentration increases, leading to a reduction of the band gap and finally to a metallic state. This goes hand in hand with an increase of the lattice constant.

Experimental and First-Principles Studies of the Band Alignment at the HfO2/4H-SiC (0001) Interface

2006 ◽  
Vol 527-529 ◽  
pp. 1071-1074 ◽  
Author(s):  
Carey M. Tanner ◽  
Jong Woo Choi ◽  
Jane P. Chang
Keyword(s):  
Conduction Band ◽  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Atomic Layer ◽  
Band Alignment ◽  
Functional Theory ◽  
X Ray ◽  
Conduction Band Offset ◽  
Mos Devices ◽  
Layer Deposition

The electronic properties of HfO2 films on 4H-SiC were investigated to determine their suitability as high-κ dielectrics in SiC power MOS devices. The band alignment at the HfO2/4HSiC interface was determined by X-ray photoelectron spectroscopy (XPS) and supported by density functional theory (DFT) calculations. For the experimental study, HfO2 films were deposited on ntype 4H-SiC by atomic layer deposition (ALD). XPS analysis yielded valence and conduction band offsets of 1.69 eV and 0.75 eV, respectively. DFT predictions based on two monoclinic HfO2/4HSiC (0001) structures agree well with this result. The small conduction band offset suggests the potential need for further interface engineering and/or a buffer layer to minimize electron injection into the gate oxide.

Supramolecular Organization and Evaporation of Polymeric Tin Trifluoroacetates

2019 ◽  
Author(s):  
Goran Bacic ◽  
Conor D. Rankine ◽  
Jason D. Masuda ◽  
Derek A. Wann ◽  
Sean Barry
Keyword(s):  
Thermal Stability ◽  
Solid State ◽  
Density Functional ◽  
Chemical Vapor ◽  
Atomic Layer ◽  
Building Blocks ◽  
Supramolecular Organization ◽  
Layer Deposition ◽  
Earth Abundant ◽  
Green Potential

<div> <div> <div> <p>Simple tin carboxylates make up a family of important industrial catalysts and precursors for deposition of SnO2 thin films. However, their structures remain disparately characterized, and tin trifluoroacetates have been particularly elusive. Here we report on a combined X-ray diffraction (XRD), gas phase electron diffraction (GED) and density functional theory (DFT) study into the structure and bonding of tin(II) and tin(IV) trifluoroacetates to understand their influence on thermal stability and volatility. Tin(II) bis(trifluoroacetate) (1′) eliminates trifluoroacetic anhydride upon sublimation to form the linear polymeric hexatin(II)-di-μ -oxy-octakis-μ-trifluoroacetate (1F ), which itself sublimes (1 Torr at 191 C) as a 1:1 mixture of 1 and ditin(II)-μ-oxy-bis-μ-trifluoroacetate (1′′). Tin(IV) tetrakis(trifluoroacetate) (2F) is also polymeric in the solid state, but evaporates as a monomer at low temperatures (1 Torr at 84 ◦C). Together they make a family of multifunctional Lewis acidic and basic building blocks for supramolecular organization of clusters and polymers in the solid state. Anomalous trends in the volatility of these trifluoroacetates and their hydrogenated derivatives can be rationalized by consideration of their modes of polymerization with respect to the thermodynamics of evaporation. Both 1F and 2F combine high thermal stability and volatility, and are demonstrated to be complementary, safe, and green potential precursors for chemical vapor deposition (CVD) or atomic layer deposition (ALD) of earth-abundant transparent conducting F-doped SnO2. </p> <div><div><div> <p> </p> </div> </div> </div> </div> </div> </div>

The Competitive Reactions in Atomic Layer Deposition of HfO2, ZrO2 and Al2O3 on Hydroxylated Si(100) Surfaces: A Density Functional Theory Study

2011 ◽  
Vol 675-677 ◽  
pp. 1249-1252
Author(s):  
Jie Ren ◽  
Guang Fen Zhou
Keyword(s):  
Density Functional Theory ◽  
Atomic Layer Deposition ◽  
Density Functional ◽  
Surface Reactions ◽  
Atomic Layer ◽  
Density Functional Theory Study ◽  
Geometrical Structures ◽  
Functional Theory ◽  
Competitive Reactions ◽  
Layer Deposition

The competitive reactions in atomic layer deposition (ALD) of HfO2, ZrO2 and Al2O3 on the hydroxylated Si(100) surfaces are investigated by using density functional theory. The surface reactions in ALD of HfO2 and ZrO2 show large similarities in energetics and geometrical structures. However, both of them show discrepancies with the surface reactions in ALD of Al2O3. In addition, by comparing with the self-termination reactions, we could find that the further growth reactions are both kinetically and thermodynamically more favorable in ALD of HfO2, ZrO2 and Al2O3.

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