Alkali-Metal Containing Amorphous Carbon: Reactivity and Electronic Structure

1999 ◽  
Vol 593 ◽  
Author(s):  
M. Töwe ◽  
P. Reinke ◽  
P. Oelhafen
Keyword(s):  
Electronic Structure ◽  
Alkali Metal ◽  
Work Function ◽  
Photoelectron Spectroscopy ◽  
Alkali Metals ◽  
Film Surface ◽  
Carbon Films ◽  
Metal Atoms ◽  
Sample Characterization

ABSTRACTAmorphous hydrogen-free carbon films (sp2-dominated a-C) were deposited under ultrahigh vacuum conditions between room temperature and 800°C. These films served as matrices for the in-situ incorporation of alkali-metal atoms (Li, Na). In-situ sample characterization was performed by photoelectron spectroscopy with both x-ray and ultraviolet excitation (XPS, UPS). While the clean metal-containing samples were prepared with metal contents of about 10 at%, a strong oxidation driven accumulation of metal atoms on the film surface exceeding 50 at% was observed upon exposure to molecular oxygen. Work-function measurements by UPS reflected the changes within the electronic structure of the material. Metal incorporation considerably decreased the work-function, but only after oxidation we observed work-functions below the values given for pure alkali metals.

ELECTRONIC AND STRUCTURAL PROPERTIES OF Si–Gd–O ELECTRON EMITTER

2019 ◽  
Vol 27 (01) ◽  
pp. 1950089
Author(s):  
M. I. FEDORCHENKO ◽  
P. V. MELNIK ◽  
M. G. NAKHODKIN ◽  
O. I. GUDYMENKO ◽  
V. P. KLADKO ◽  
...  
Keyword(s):  
Rare Earth ◽  
Work Function ◽  
Photoelectron Spectroscopy ◽  
Alkali Metals ◽  
Rare Earth Metals ◽  
Film Surface ◽  
Surface Region ◽  
Kelvin Probe ◽  
Surface Distribution ◽  
Near Surface

Rare earth metals, when deposited and oxidized on semiconductor surfaces, can be an alternative to unstable compounds of alkali metals while creating stable and effective emitters with a low work function. A procedure giving rise to the adsorption of Gd and O atoms on the Si(100) surface and the formation of a Si–Gd–O film with a work function of about 1 eV in the near-surface region is described. The films have been studied using the Auger electron and photoelectron spectroscopy, as well as X-ray diffraction, atomic force and Kelvin probe force microscopy techniques. Information about their electronic properties, structure, surface morphology, and surface distribution of potential was obtained. The main component of the film formed on the Si surface is a polycrystalline Gd2O3 phase, which plays the role of a matrix containing textured microcrystallites of one of the following phases: SiO2, GdO2, or GdSi2. The film surface consists of salient clusters 20[Formula: see text]nm to 80[Formula: see text]nm in diameter and up to 20[Formula: see text]nm in height, as well as craters up to 90[Formula: see text]nm in depth. The surface relief inhomogeneities correlate with the surface distribution of the local work function. This correlation can also be a result of the piezoelectric effect in the strained crystallites of the textured phase located in the bulk of the film. The obtained system was stable in time under vacuum conditions and heating up to [Formula: see text]C. The method proposed for the formation of surfaces with a low work function making use of rare earth metals can be applied to create effective and stable electron emitters.

The Valence Electronic Structure of N-Doped P-Sexiphenyl

1999 ◽  
Vol 561 ◽  
Author(s):  
U. Theissl ◽  
E.J.W. List ◽  
N. Koch ◽  
A. Vollmer ◽  
S. Schrader ◽  
...  
Keyword(s):  
Thin Films ◽  
Electronic Structure ◽  
Binding Energy ◽  
Alkali Metal ◽  
Photoelectron Spectroscopy ◽  
Organic Molecule ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Surface Yield ◽  
Valence Electronic Structure

ABSTRACTThin films of p-sexiphenyl (6P) were doped with increasing amounts of potassium in situ, and the change in the valence electronic structure of 6P upon the alkali metal deposition was followed with ultraviolet photoelectron spectroscopy. We observe the evolution of new intragap emissions, which are attributed to the formation of bipolarons, even for very low doping concentrations. The low binding energy intra-gap emission exhibits a pronounced asymmetric lineshape, in contrast to the findings when cesium is used as dopant. In order to investigate whether this lineshape is due to different emissive electronic species in the bulk and on the surface of the 6P film the take-off angle for the photoelectrons was varied. As no change in the lineshape is found when going from normal to near-grazing emission we can exclude that charged 6P molecules in the bulk and on the surface yield different valence electronic spectra. Therefore, the characteristic lineshape of the low binding energy emission is proposed to be related to the interaction of the doped organic molecule with the different counterions.

scholarly journals Gently Does It!: In Situ Preparation of Alkali Metal - Solid Electrolyte Interfaces for Photoelectron Spectroscopy

2021 ◽  
Author(s):  
Joshua Gibson ◽  
Sudarshan Narayanan ◽  
Jack Swallow ◽  
Pardeep Kumar-Thakur ◽  
Mauro Pasta ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Photoelectron Spectroscopy ◽  
Alkali Metals ◽  
Organic Liquid ◽  
Single Layer ◽  
Metal Deposition ◽  
Single Layer Graphene ◽  
Energy Storage Devices ◽  
Electrolyte Interface

The key charge transfer processes in energy storage devices occur at the electrode-electrolyte interface, which is typically buried making it challenging to access the interfacial chemistry. In the case of Li-ion batteries, metallic Li electrodes hold promise for increasing energy and power densities, and when used in conjunction with solid electrolytes (SEs) adverse safety implications associated with dendrite formation in organic liquid electrolytes can potentially be overcome. To better understand the stability of SEs when in contact with alkali metals and the reactions that occur, here we consider the deposition of thin (~10 nm) alkali metal films onto SE surfaces, that are thin enough that X-ray photoelectron spectroscopy can probe the buried electrode-electrolyte interface. We highlight the importance of in situ alkali metal deposition, by assessing the contaminant species that are present after glovebox handling and the use of ‘inert’ transfer devices. Consequently, we compare and contrast three available methods for in situ alkali-metal deposition; Li sputter deposition, Li evaporation, and Li plating induced by e− flood-gun irradiation. Studies on both a sulphide SE (Li6PS5Cl), and a single-layer graphene probe surface reveal that the more energetic Li deposition methods, such as sputtering, can induce surface damage and interfacial mixing that is not seen with thermal evaporation. This indicates that appropriate selection of the Li deposition method for in situ studies is required to observe representative behaviour, and the results of previous studies involving energetic deposition may warrant further evaluation.

scholarly journals Effect of the sample work function on alkali metal dosing induced electronic structure change

2021 ◽  
pp. 147045
Author(s):  
Saegyeol Jung ◽  
Yukiaki Ishida ◽  
Minsoo Kim ◽  
Masamichi Nakajima ◽  
Shigeyuki Ishida ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Alkali Metal ◽  
Work Function ◽  
Structure Change

CO2 Adsorption on the B12N12 Nanocage Encapsulated with Alkali Metals: A Density Functional Study

NANO ◽  
2019 ◽  
Vol 14 (03) ◽  
pp. 1950034
Author(s):  
Ximin Liang ◽  
Qiyan Zhang ◽  
Qinfu Zhao ◽  
He Zhao ◽  
Yifan Feng ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Density Functional ◽  
Alkali Metals ◽  
Large Change ◽  
Functional Study ◽  
Functional Theory ◽  
Metal Atoms ◽  
Adsorption Of Co ◽  
Physical And Chemical ◽  
Homo Lumo

Density functional theory (DFT) calculations have been carried out to study the capacity of the B[Formula: see text]N[Formula: see text] nanocage encapsulated with alkali metals (Li, Na, K) for the CO2 adsorption and activation. It is found that after encapsulating alkali metals, the alkali metal atoms are closer to one side of clusters instead of exactly lying at the center, and a considerable charge transfers from the inner alkali metal atoms to the B[Formula: see text]N[Formula: see text] cage. Besides, the HOMO–LUMO gap (HLG) values of Li@B[Formula: see text]N[Formula: see text], Na@B[Formula: see text]N[Formula: see text] and K@B[Formula: see text]N[Formula: see text] are decreased to about 6[Formula: see text]eV, being much smaller than that of the pristine B[Formula: see text]N[Formula: see text]. Although the geometry structure parameters and the energy differences of M06-2X are slightly different from the ones of [Formula: see text]B97X-D, some identical results of two kinds of functional can be obtained. CO2 can be adsorbed chemically and physically on majority bonds of all the clusters, except for some bonds with large change in bond length and bond indices. The encapsulation of alkali-metal atoms may enhance the physical and chemical adsorption of CO2 on the surface of the clusters, in which Na@B[Formula: see text]N[Formula: see text] and K@B[Formula: see text]N[Formula: see text] are the most powerful physical and chemical adsorbent for CO2, respectively.

scholarly journals Thermal Stability of Octadecyltrichlorosilane and Perfluorooctyltriethoxysilane Monolayers on SiO2

Nanomaterials ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 210
Author(s):  
Xiangdong Yang ◽  
Haitao Wang ◽  
Peng Wang ◽  
Xuxin Yang ◽  
Hongying Mao
Keyword(s):  
Thermal Stability ◽  
Thermal Behavior ◽  
Work Function ◽  
Photoelectron Spectroscopy ◽  
Vacuum Annealing ◽  
Moderate Temperature ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
X Ray ◽  
Thermal Stability Of

Using in situ ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) measurements, the thermal behavior of octadecyltrichlorosilane (OTS) and 1H, 1H, 2H, and 2H-perfluorooctyltriethoxysilane (PTES) monolayers on SiO2 substrates has been investigated. OTS is thermally stable up to 573 K with vacuum annealing, whereas PTES starts decomposing at a moderate temperature between 373 K and 423 K. Vacuum annealing results in the decomposition of CF3 and CF2 species rather than desorption of the entire PTES molecule. In addition, our UPS results reveal that the work function (WF)of OTS remains the same after annealing; however WF of PTES decreases from ~5.62 eV to ~5.16 eV after annealing at 573 K.

In situ work-function measurement during chemical transformation of MoS2 to MoO3 by ambient-pressure x-ray photoelectron spectroscopy

2D Materials ◽  
2020 ◽  
Vol 7 (2) ◽  
pp. 025014
Author(s):  
Dooyong Lee ◽  
Jae Hyuck Jang ◽  
Wooseok Song ◽  
Joonhee Moon ◽  
Yooseok Kim ◽  
...  
Keyword(s):  
Work Function ◽  
Chemical Transformation ◽  
Photoelectron Spectroscopy ◽  
Ambient Pressure ◽  
Function Measurement ◽  
X Ray

Preparation and Characterization of Chromium Containing amorphous Hydrogenated Carbon Films (A-C:H/Cr)

1995 ◽  
Vol 388 ◽  
Author(s):  
R. Gampp ◽  
P. Gantenbein ◽  
P. Oelhafen
Keyword(s):  
Chromium Carbide ◽  
Photoelectron Spectroscopy ◽  
Chemical Vapor ◽  
Carbon Films ◽  
Rf Plasma ◽  
Silicon Substrates ◽  
Amorphous Hydrogenated Carbon ◽  
High Chemical Stability

AbstractChromium containing amorphous hydrogenated carbon films (a-C:H/Cr) were prepared in a process that combines rf plasma activated chemical vapor deposition of methane and magnetron sputtering of a chromium target. During the deposition the silicon substrates were kept at 200°C and dc biased at -200 V in order to obtain films with high chemical stability which is required for the application as solar selective surfaces. the films with different Cr concentrations (5 to 49 at.%) were characterized by in situ x-ray photoelectron spectroscopy (XPS). Up to 40 at.%, chromium proves to be built into the cermet-like films in the form of chromium carbide clusters. above 40 at.%, chromium is partly metallic. a modification of the a-C:H matrix in the vicinity of the chromium carbide clusters has been observed.

Experimental evidence from liquid semiconductors

1977 ◽  
Vol 55 (11) ◽  
pp. 1961-1967 ◽  
Author(s):  
J. E. Enderby
Keyword(s):  
Electronic Structure ◽  
Alkali Metal ◽  
Experimental Evidence ◽  
Atomic Structure ◽  
Alkali Metals ◽  
The Other ◽  
Ionic Bonding ◽  
Liquid Semiconductors ◽  
Close Interaction ◽  
Semiconducting Alloys

Two broad types of liquid semiconducting alloys will be discussed, namely those involving alkali metals (e.g., the Li–Pb and the Cs–Au system) and those in which a chalcogen is involved (e.g., Cu–Te or Ni–Te). It will be argued that relatively simple ionic bonding schemes in alkali metal systems must be replaced by more complicated ones in chalcogen based alloys. The close interaction between atomic structure on one hand, and the electronic structure on the other will be emphasized.

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