Work-function changes accompanying changes in composition of (100) surfaces of HfCx and TaCx

Gruzalski, G.R.; Lui, S.-C.; Zehner, D. M.

doi:10.1016/0039-6028(90)90608-b

Cited by 25 publications

(5 citation statements)

References 5 publications

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“…Figure shows the calculated work functions of the {100} surface of TMC 1– x O x (TM = Ti–Ta) at x = 0, 0.25, and 0.5. The calculated values for TMCs ( x = 0) are within approximately ±0.5 eV from experimental values, and ±0.2 eV from theoretical values. − The differences from the experimental values are likely to be attributed to carbon defects in TMCs. − In the early stage of oxidation as x increases from 0 to 0.25, the work function greatly reduces for all these TMCs, which agrees well with our experimental results that the work function of HfC and ZrC reduces from 3.6 to 2.5 eV and from 3.6 to 3.02 eV, respectively. , In the case of HfC 1– x O x , x was estimated to be approximately 0.2 . In the experiments, − the ⟨100⟩ oriented nanowires were sharpened by field evaporation when surfaces other than the {100} surface may have appeared.…”

Section: Results and Discussionsupporting

confidence: 84%

Reduction in Work Functions of Transition-Metal Carbides and Oxycarbides upon Oxidation

et al. 2021

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Herein, the work functions of group 4 and group 5 transition-metal (Ti, Zr, Hf, V, Nb, and Ta) carbides and transition-metal oxycarbides (TMCOs) were investigated by first-principles calculations for their potential application as electron emitters. The work functions of both groups decreased as the substitution of carbon atoms with oxygen proceeded, and the reduction in group 4 was more than that of group 5. In particular, ZrC1–x O x and HfC1–x O x (x ≥ 0.25) exhibited work functions of less than 3 eV, which were comparable with those of LaB6- and ZrO-coated tungsten. The reduction in the work functions could be explained by the rigid-band model of the electronic density of states. The increase in valence electrons increased the Fermi energy, while it demonstrated a less significant influence on the vacuum potential, resulting in a reduction in the work functions. The phonon dispersion curves indicated that the NaCl-type group 5 TMCOs were less stable than the group 4 TMCOs. This agrees with the experimental findings that TaC1–x O x was not synthesized and NbC1–x O x was synthesized only for smaller values of x (i.e., x < 0.28). From the viewpoints of the work functions and structural stabilities, group 4 (Ti, Zr, and Hf) TMCOs exhibit better potential for application as electron emitters than group 5 (V, Nb, and Ta) TMCOs.

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Section: Results and Discussionsupporting

confidence: 84%

Reduction in Work Functions of Transition-Metal Carbides and Oxycarbides upon Oxidation

et al. 2021

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“…The image is highly uniform across the surface with work functions values of 4.0 ± 0.02 eV. These values are higher than what has been reported for HfC, [3.87 eV] [27] or Hf metal [3.95 eV] [28] and slightly lower than values reported for graphene on SiC. [29] The structural and electronic characteristics of the surface are further evidence for graphene formation as a result of the CMBE process.…”

Section: Resultsmentioning

confidence: 60%

Direct graphene growth on transitional metal with solid carbon source and its converting into graphene/transitional metal oxide heterostructure

Park

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Fairchild

et al. 2017

Carbon

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International audienceThe oxide/semiconductor structure is key to controlling current in electronic devices and HfO$_2$ is a common gate material in conventional electronic devices due to its favorable dielectric properties. Graphene devices also require insulating gates. We demonstrate a unique direct growth approach to obtain the bottom gate structure (graphene/HfO$_2$/n-SiC). The present approach involves transfer of graphene grown by chemical vapor deposition (CVD) on Cu to oxidized Si wafers, a complex process prone to low yield and reduced performance. Furthermore, HfO$_2$ is preferred to SiO$_2$ because of its superior properties. The proposed concept consists of the direct deposition of graphene by solid carbon molecular beam epitaxy on Hf metal coated n-type SiC, followed by oxygen intercalation to form HfO$_2$. The oxygen intercalation will then convert the underlying Hf into HfO$_2$ due to the strong affinity of Hf with oxygen. We identify the graphene/HfO 2 formation by Raman, X-ray photoelectron spectroscopy (XPS), Low energy electron diffraction (LEED), Low energy electron microscopy (LEEM) and electrical properties including Hall mobility and leakage current measurement

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“…We validate our computational approach by performing sets of work function calculations on pure transition metals as well as binary transition metal carbides and nitrides [77]. The results were compared with the available theoretical and experimental data [79][80][81][82][83][84][85][86][87][88][89][90][91].…”

Section: Calculation and Analysis Methodmentioning

confidence: 99%

OH-terminated two-dimensional transition metal carbides and nitrides as ultralow work function materials

et al. 2015

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Work-function changes accompanying changes in composition of (100) surfaces of HfCx and TaCx

Cited by 25 publications

References 5 publications

Reduction in Work Functions of Transition-Metal Carbides and Oxycarbides upon Oxidation

Reduction in Work Functions of Transition-Metal Carbides and Oxycarbides upon Oxidation

Direct graphene growth on transitional metal with solid carbon source and its converting into graphene/transitional metal oxide heterostructure

OH-terminated two-dimensional transition metal carbides and nitrides as ultralow work function materials

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