Search query: Controlled Etching of Au:SR Cluster Compounds

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abstract: When Au:SR cluster compounds (R (CH2)5CH3) with an Au metallic cluster core mass of ~14 kDa ~75 atoms, 1.1 nm equivalent diameter) are heated in neat dodecane thiol solution under inert atmosphere, species with smaller Au core masses are formed, presumably by the removal of Au atoms from the outermost surface layer of the cluster's Au core. This process was monitored through laser desorption mass spectrometry, optical absorption spectroscopy, and X ray diffraction, where all three methods indicate a substantial decrease >50% by mass or number of Au atoms) in the size of the cluster compound's inorganic core. The optical absorption spectra and laser desorption mass spectra of the compounds generated by etching are strikingly similar to compounds previously separated without an etching step. The dual function of the thiol as both stabilizing adsorbate and efficient etchant sets this cluster (or nanocrystal) system apart from other metallic and semiconductor systems.
author_names: +++ and T Gregory Schaaff

Robert L Whetten
title: Controlled Etching of Au:SR Cluster Compounds
year: 1999

abstract: Two hybridized skeleton borates [Zn(en)2][B7O12(OH) (1; en ethylenediamine) and [Cd(1,3 dap)2][B5O8(OH)*H2O (2; 1,3 dap 1,3 diaminopropane) were solvothermally synthesized. The boron oxide clusters formed 2D planes, and these planes formed a 3D structure through co oxygen links of metal complexes. Herein, a novel strategy has been developed, i.e. the derived guest carbon materials from semi decomposed borate are incorporated into the void of host borate crystals in situ during the thermal etching process. Moreover, the effect of temperature on fluorescence of derived carbon materials was studied. By controlling the calcining temperature, carbon dots with obvious free radicals can be found via ESR technique. Carbon dots in the ethanol phase exhibited variable photoluminescence. Furthermore, it derived semi decomposition carbon materials via thermal etching based on compounds 1 and 2. In an hydrogen cell reactor, carbon material Zn based catalyst 1 200 catalyzes CO2 reduction to CO with a selectivity that reaches 50.8% at 1.4 V vs RHE.
author_names: Ying Liu

Kang Zhou

Hong-li Chen

Yun-Nan Gong

Chun-Yang Pan
title: A Way for Derived Carbon Materials by Thermal Etching Hybrid Borate for Electrochemical CO2 Reduction.
venue: Inorganic chemistry
year: 2020

abstract: The progress of research focused upon the etching of metal films or substrates using fluorine gases has been restricted by limited information regarding etching reactants and byproducts. Indeed, aspects of the etching mechanism itself remain unclear. In this study, a new reactive force field (ReaxFF) for Al F was developed to describe the interaction and reactions in Al F materials. The ReaxFF accurately reproduces the quantum mechanics derived training set for structures and energies of gaseous AlFx molecules and Al F crystals. Based on this Al F ReaxFF, the effects of chemical source (F/Al 1 6) and temperature (1000 1500 K) on the etching product and rate were studied. The formation of gaseous AlFx was revealed in five steps with the fluorine concentration being the prime factor affecting the etching products. Below the critical concentration ratio of F/Al 3, where the chemical driving force is insufficient, only four of the five steps occur and a AlFx cluster is formed without significant gaseous species; above this critical concentration, a fifth step happens, and isolated AlFx gaseous phases with much more negative formation energies, such as AlF4, AlF5, and AlF6, can be formed. Besides this concentration ratio, external parameters such as elevated temperature or higher voltage dischage may be an important energetic factor affecting the product quantity. These results may provide insights into controlling the formation kinetics of specific AlFx compounds or gaseous phases for the preparative chemistry of Al F porous catalyst, and the Al F ReaxFF provides a useful tool for studying the interaction and reaction of Al F materials at the atomic scale.
author_names: Yongli Liu

Yang Qi

Xian-quan Hu

Adri C T Duin
title: Formation of AlFx Gaseous Phases during High Temperature Etching: A Reactive Force Field Based Molecular Dynamics Study
year: 2019

abstract: The synthesis of cluster based materials poses an exciting challenge for experimental chemistry. The main advantage of these materials compared to conventional bulk compounds is the simple tunability of the chemical and physical characteristics of individual clusters. As a consequence, cluster assemblies can theoretically be used for the creation of designer materials exhibiting specifically desired properties. Since superatoms reveal a large intrinsic thermodynamic stability and often very interesting tunable electronic characteristics, they seem to be an excellent choice as building blocks for the bulk. Here, we present a detailed first principles analysis of carefully chosen superatomic cluster binary and bulk assemblies, in order to determine which forces control the attractive interaction in superatomic solids, and how the individual cluster properties affect these assemblies. This study uses the highly tunable and stable Au13(RS(AuSR)2)6 cluster with a variety of dopants as a model system, while the principles are likely transferable to other ligand protected systems with a straightforward superatomic electron count, such as aluminum or sodium clusters. Three different superatomic materials based on doped gold clusters, boranes and C60s are constructed and evaluated. Beyond the verification that superatoms can be used to create materials that reveal emergent atom based solid like properties, various factors influencing superatomic materials, such as the EA, IP and relative sizes of the clusters, have been identified and critically evaluated.
author_names: Julia Schacht

Nicola Gaston
title: Cluster assemblies as superatomic solids: a first principles study of bonding electronic structure.
venue: Physical chemistry chemical physics PCCP
year: 2018

abstract: Abstract 10 nm scale Si pillars were fabricated using deposited Au, Ag, Cu clusters and colloidal Au particles as nuclei for formation of etch masks in SF6 microwave plasma etching at about 130degC. The pillar diameter is affected by the chemical species of the clusters, but is only weakly dependent on the cluster size. The average diameter of pillars fabricated with Au clusters is 9 nm, while those with Ag and Cu clusters are 19 and 24 nm, respectively. This is considered to be due to the difference in stability of the compounds of Au, Ag, and Cu with S or F, the components of the etching gas, which results in a different ability to form etch masks by condensation of SxFy species.
author_names: Tetsuya Tada

Toshihiko Kanayama

Kenji Koga

Katrin Seeger

S J Carroll

Pascal Weibel

Richard E Palmer
title: Fabrication of size controlled 10 nm scale Si pillars using metal clusters as formation nuclei
year: 1998

abstract: Immersion of atomically flat, H terminated Si(111) surfaces in 7.6 M HI for 0.5 4 h caused spontaneous formation of nanosized clusters at the Si surface. X ray photoelectron spectroscopy analysis suggested that the clusters were composed of silicon iodides (such as SiHxI4 x) produced most probably by Si etching with HI. Atomic force microscopy inspection revealed that the immersion at a low temperature below about 30 degrees C led to the formation of long rod shaped clusters, oriented in the (112) direction or equivalents, whereas the immersion at a high temperature above 30 degrees C led to the formation of circular dot clusters, their size and shape changing abruptly at about 70 degrees C. It is shown experimentally that the formation of dot clusters at a high immersion temperature is explained on the basis of thermodynamics, whereas that of oriented rod clusters at a low temperature is explained by a kinetics controlled mechanism.
author_names: Akihito Imanishi

Takeshi Hayashi

Yoshihiro Nakato
title: Temperature dependence of formation of nanorods and dots of iodine compounds on an H terminated Si(111) surface in a concentrated HI solution.
venue: Langmuir the ACS journal of surfaces and colloids
year: 2004

abstract: Abstract The central theme of the project involved the interaction of ionized beams with solid surfaces. Such studies are relevant to materials synthesis problems because advanced manufacturing processes involve thin film growth and etching under conditions where energetic ions and clusters are present. While it is known that these ions play an important role, the details of their interactions are poorly understood. A significant part of the program during this funding period dealt with the development of instrumentation that would allow the formation of a beam of ionized clusters, the selection from that beam of those clusters that had a particular mass and energy, and then the deposition of those clusters onto a surface with full control over the parameters of deposition. The source was successfully built and tested. The goal was to study the atomic scale processes of this ionized cluster beam deposition (ICBD) The plan was to use scanning tunneling microscopy to characterize the clusters that were deposited and to determine the effect on the surface as a function of cluster energy and cluster size. jg p.6
author_names: John H Weaver
title: Thin Film Growth with Ions, Clusters, and Metal Compounds.
year: 1995

abstract: Method validation in capillary electrophoresis (CE) is substantial for the routine use in quality control. Thus all phenomena that can influence results in CE must be carefully characterised. Especially the inner surface of the fused silica capillaries plays an important role. Sometimes there is a big difference in the properties of capillaries from different batches. Inner capillary surface can be pictured by scanning electron microscopy (SEM) Nature, pattern and number of cracks and other surface defects altered from batch to batch. These surface defects were no artefacts of sample preparation, which could be excluded by comparing different preparation techniques and results from literature. Treatments with hydrofluoric acid cannot completely remove the surface cracks and defects in subsurface areas. Hydrofluoric acid treatment not only changes the surface roughness but also the inner capillary diameter. A correlation between etching time and increase of diameter is investigated. SEM also pictures adsorption phenomena, e.g. proteins are not adsorbed as a homogenous layer. Clusters at different regions are observed. Thus the z potential differs considerably with space, leading to losses in separation efficiency. SEM can readily be used to analyse the effectiveness of rinsing procedures. There are residuals of adsorbed compounds even after using aggressive rinsing reagents.
author_names: Stefan Kaupp

Ronald W Steffen

Hermann Watzig
title: Characterisation of inner surface and adsorption phenomena in fused silica capillary electrophoresis capillaries
year: 1996

abstract: Abstract Over the past four years the University of Massachusetts Photonics Center, the Center for Advanced Materials and the Submillimeterwave Technology Laboratory in partnership with AFRL/SNHC has been developing technology for producing low defect density substrates and high quality epi substrate interfaces for ABCS device applications as well as developing fabrication and device concepts for incorporation into quantum cascade THz lasers. During the course of the project a number of new technologies were developed and demonstrated. A new Bridgeman magnetic stirring antimonide bulk growth method was developed and using the method uniformly selinium n type doped bulk GaSb crystals were grown; Bulk InGaSb crystals were grown; and GaAlSb bulk crystals were grown. In the areas of wafer polishing and epi substrate interface control, novel gas cluster ion beam (GCIB) final polishing methods and bromine ion beam assisted etching final polishing methods were developed that allow control of the epi substrate interface when molecular beam epitaxy is employed for epigrowth. In the THz portion of the project novel Thz photonic crystals were demonstrated and new phonon mediated THz quantum cascade laser design developed. The ABCS polishing work was moved toward commercialization through two joint collaborations with Galaxy Compound Semiconductors, Inc, a Phase I SBIR to develop bromine based GaSb GCIB polishing (AFRL) and a PhaseI/II project to develop novel final polishing techniques for GaSb and InSb wafers (DARPA) The THz work generated collaborations with Drs. T. Nelson and J.Ehret of WPAFB, Prof. Ram Mohan of WPI/Quantum Semiconductor Algorithms, Inc. and Dr. Kurt Linden of Spire Corp.
author_names: William D Goodhue

David Francis Bliss

Kannan Krishnaswami

Shivashankar Vangala

Jin Li

B Zhu
title: Low Defect Density Substrates and High Quality Epi Substrate Interfaces for ABCS Devices and Progress Toward Phonon Mediated THz Lasers
year: 2005

abstract: Abstract Currently, oxygen atoms are intentionally introduced in Si crystals during Czochralski (CZ) pulling process. They usually come from a controlled out diffusion from the crucible, the expected role of these impurities being to generate silicon oxide clusters or micro precipitates. Afterwards, these small aggregates are able to getter residual metallic impurities which are introduced into the wafer during the integrated circuit fabrication process. This operation is called "internal gettering" and its successive steps, from "embryo" nucleation to precipitate condensation, require an adapted control adjustment. Convenient thermal cycles reduce the amount of metallic doping in the vicinity of the ICs, thus improving specifications such as diode leakage current or minority carrier lifetime or premature oxide breakdown. This is a key problem in VLSI technology as well as in CCDs. It is also worth noting that the device process itself (annealing) participates in the final texture of precipitates and in the dimension of the "precipitate free zone" (or denuded zone) underlying the wafer surface.Experimental means for observing the individual precipitates and their spatial distribution are not so diversified. X rays, EBIC or chemical etching are used to obtain images of these defects. The latter technique is the most widely used but not so precise; three dimensional exploration requires delicate preparation such as controlled bevel etching. It is also known that not all species of precipitates can be revealed by etching. Recently, a new technique called "laser scanning tomography" (LST) has been proposed. It consists of scanning the bulk of the wafer with a thin laser probe beam along a virtual plane; the scattered light image is recorded with a camera and computer reconstructed. LST is non destructive, very sensitive to all kinds and sizes of microprecipitates and has three dimensional capability; it does not need any special and time consuming preparation or vacuum conditions. Internal structures such as depleted zone (DZ) or striations or layered structures are easily detected and measured. Both qualitative (profiles, features) and quantitative (densities, size, dimensions, classification) information is obtained from LST images. LST has previously been used for III V compound defect analysis. In this communication we report the present state of the art of the investigations on CZ silicon.
author_names: J P Fillard
title: Investigations of oxygen precipitates in Czochralski silicon wafers by using infrared tomography
year: 1990