BEEM imaging and spectroscopy of buried structures in semiconductors

Narayanamurti, V.; Kozhevnikov, Maria

doi:10.1016/s0370-1573(00)00119-8

Cited by 80 publications

(63 citation statements)

References 132 publications

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“…This depends on the electron path length through the metal film and is energy dependent. Its functional form is an exponential decay [11]. The third step is the transmission across the interface, and depends on the energy and direction of the electrons.…”

Section: Discussionmentioning

confidence: 99%

Metal–organic interfaces at the nanoscale

et al. 2004

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In this work, we present an investigation of the Ag-PPP (polyparaphenylene) interface using ballistic electron emission microscopy. Our work is the first successful application of the BEEM technique to metal-organic interfaces. We observe nanometer scale injection inhomogeneities. They have an electronic origin, since we find corresponding Schottky barrier variations. We also determine the transmission function of Ag-PPP interface and find that it agrees qualitatively with the theoretical calculations for a metalphenyl ring interface. We conclude that charge transport across inhomogeneous barriers needs to be considered for understanding electronic transport across metal-organic interfaces and organic device characteristics.

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Section: Discussionmentioning

confidence: 99%

Metal–organic interfaces at the nanoscale

et al. 2004

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“…1(b)]. As can be seen in the spectrum in 1(a), the yield of the BEEM electrons is remarkably high, compared to values reported in the literature [22][23][24] for other metal-semiconductor interfaces.…”

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confidence: 69%

Conservation of the Lateral Electron Momentum at a Metal-Semiconductor Interface Studied by Ballistic Electron Emission Microscopy

Bobisch

Bannani²,

Koroteev³

et al. 2009

Phys. Rev. Lett.

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We report on ballistic electron emission microscopy and spectroscopy studies on epitaxial (3-5 nm thick) Bi(111) films, grown on n-type Si substrates. The effective barrier heights of the Schottky barrier observed are 0.58 eV for the Bi=Sið100Þ-ð2 Â 1Þ and 0.68 eV for the Bi=Sið111Þ-ð7 Â 7Þ. At the step edges of the epitaxial films a strong increase of the ballistic electron emission microscopy current is observed for Bi=Sið111Þ-ð7 Â 7Þ, while no increase occurs for Bi=Sið100Þ-ð2 Â 1Þ. These observations can be explained by the conservation of the lateral momentum of the electron at the metal-semiconductor interface. DOI: 10.1103/PhysRevLett.102.136807 PACS numbers: 73.23.Ad, 73.20.At, 73.30.+y, 73.40.Àc Since the invention of ballistic electron emission microscopy (BEEM) by Bell and Kaiser two decades ago [1,2], studies on the conservation of lateral electron momentum at the interface formed between metals and semiconductors have remained puzzling. Schowalter and Lee [3,4] studied ballistic electron emission spectroscopy (BEES) for Au films grown on Si substrates with different crystallographic orientations. Assuming that the lateral electron momentum at the metal-semiconductor interface is conserved [2] the BEEM currents were expected to differ dramatically due to different projections of the conduction band minima of the Si on the (111) and (100) plane. However, almost identical BEEM currents were measured. These results were later confirmed by Weilmeier et al. [5,6]. In the case of Pd on Si, Ludeke and Bauer [7] attributed the observed equality of transmission across (111) and (100) to interface scattering randomizing the electron momentum. As discussed by García-Vidal et al.[8] and Bell [9], the results found on Au samples may be explained without additional electronic scattering processes, because the electronic band structure of the transition metals (Au, Ag, Pd, etc.) exhibits a band gap in the [111] direction, requiring a minimal lateral component of the electronic momentum. Taking into account the matching conditions at the metal-semiconductor interface, they predicted a similar onset for the BEEM current, but a higher intensity for Au=Sið111Þ in agreement with the experiments.A different situation is found with CoSi 2 =Sið100Þ versus CoSi 2 =Sið111Þ. The band structure of CoSi 2 allows the propagation of electrons at k k ¼ 0, and due to the excellent quality of the epitaxial layers there is very little diffuse scattering of electrons. The latter is confirmed by the high resolution of detail at the metal-semiconductor interface obtained by BEEM imaging [10], indicating that the electrons are limited to a very small cone within the CoSi 2 . A theoretical description by García-Vidal et al. [8,[11][12][13][14] could explain the high spatial resolution for BEEM and has predicted that the onset for the BEEM current should be shifted for the (111) versus the (100) substrate, due to the conservation of the lateral momentum at the interface. However, the experimental results for the BEEM current are contra...

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“…We are planning to do similar measurements for InGaAs/InGaAlAs heterostructures both with and without embedded ErAs nanoparticles and investigate their role in lateral momentum scattering. It is possible to do similar three-terminal measurements with even individual nanoparticles with the use of a scanning tunneling microscope tip near the surface, a configuration that is called ballistic electron emission microscopy (BEEM) [ 23 ]. Indeed, BEEM has been used to probe the energy states of individual embedded quantum dots [ 24 ].…”

Section: Ballistic Transistor Structuresmentioning

confidence: 99%

Solid-State and Vacuum Thermionic Energy Conversion

Shakouri¹,

Bian²,

Singh³

et al. 2005

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A brief overview of the research activities at the Thermionic Energy Conversion (TEC) Center is given. The goal is to achieve direct thermal to electric energy conversion with >20% efficiency and >1W/cm 2 power density at a hot side temperature of 300-650C. Thermionic emission in both vacuum and solid-state devices is investigated. In the case of solid-state devices, hot electron filtering using heterostructure barriers is used to increase the thermoelectric power factor. In order to study electron transport above the barriers and lateral momentum conservation in thermionic emission process, the currentvoltage characteristic of ballistic transistor structures is investigated. Embedded ErAs nanoparticles and metal/semiconductor multilayers are used to reduce the lattice thermal conductivity. Cross-plane thermoelectric properties and the effective ZT of the thin film are analyzed using the transient Harman technique. Integrated circuit fabrication techniques are used to transfer the n-and p-type thin films on AlN substrates and make power generation modules with hundreds of thin film elements. For vacuum devices, nitrogen-doped diamond and carbon nanotubes are studied for emitters. Sb-doped highly oriented diamond and low electron affinity AlGaN are investigated for collectors. Work functions below 1.6eV and vacuum thermionic power generation at temperatures below 700C have been demonstrated. Report Documentation Page INTRODUCTIONDirect thermal to electrical energy conversion systems that could operate at lower temperatures (300-650C) with high efficiencies (>15-20%) provide an attractive compact alternative to internal combustion engines for many applications in the W-MW range. They will also expand the possibilities for waste heat recovery applications. The Thermionic Energy Conversion Center's goal is to design, fabricate, and characterize direct energy conversion systems that meet the above requirements. The core of the solution is an integrated approach to engineer electrical and thermal properties of nanostructured materials and devices and fabricate more efficient solid-state and vacuumbased thermionic energy conversion systems. Solid-state material design is focused on increasing the efficiency of heterostructure thermionic power generators using embedded nanoparticles and metal/semiconductor superlattices. Vacuum effort focuses on the development of thermionic energy conversion based on thermionic-field emission from nanostructured carbon surfaces and low work function n-type wide band gap semiconductor collectors. Measurements of electrical, optical and thermal transport at both the device and nanostructure level are used to verify model predictions and thereby lay the foundation for improved device and materials design. Finally, various components will be integrated and packaged for systems demonstration. Fig. 1 displays a chart of the research groups participating in the Thermionic Energy Conversion Center.

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BEEM imaging and spectroscopy of buried structures in semiconductors

Cited by 80 publications

References 132 publications

Metal–organic interfaces at the nanoscale

Metal–organic interfaces at the nanoscale

Conservation of the Lateral Electron Momentum at a Metal-Semiconductor Interface Studied by Ballistic Electron Emission Microscopy

Solid-State and Vacuum Thermionic Energy Conversion

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