Solid Surfaces, Interfaces and Thin Films

Lüth, H.

doi:10.1007/978-3-642-13592-7

Cited by 258 publications

(257 citation statements)

References 0 publications

Supporting

Mentioning

248

Contrasting

Unclassified

Order By: Relevance

“…21,22 In the established picture, the electron donor character of H induces downward surface band bending that leads to a crossing of the conduction band minimum (CBM) and the Fermi level E F . As a consequence, a strongly confined surface charge accumulation layer (CAL) forms, 23 as sketched in Fig. 1(a).…”

Section: -19mentioning

confidence: 99%

Local aspects of hydrogen-induced metallization of theZnO(101¯0)surface

et al. 2015

View full text Add to dashboard Cite

This study combines surface-sensitive photoemission experiments with density functional theory (DFT) to give a microscopic description of H adsorption-induced modifications of the ZnO(1010) surface electronic structure. We find a complex adsorption behavior caused by a strong coverage dependence of the H adsorption energies: Initially, O-H bond formation is energetically favorable and H acting as an electron donor leads to the formation of a charge accumulation layer and to surface metallization. The increase of the number of O-H bonds leads to a reversal in adsorption energies such that Zn-H bonds become favored at sites close to existing O-H bonds, which results in a gradual extenuation of the metallization. The corresponding surface potential changes are localized within a few nanometers both laterally and normal to the surface. This localized character is experimentally corroborated by using sub-surface bound excitons at the ZnO(1010) surface as a local probe. The pronounced and comparably localized effect of small amounts of hydrogen at this surface strongly suggests metallic character of ZnO surfaces under technologically relevant conditions and may, thus, be of high importance for energy level alignment at ZnO-based junctions in general.

show abstract

Section: -19mentioning

confidence: 99%

Local aspects of hydrogen-induced metallization of theZnO(101¯0)surface

et al. 2015

View full text Add to dashboard Cite

show abstract

“…This forms a low-conductivity depletion layer near the surface, where the screening of piezoelectric potential by free carriers effect is suppressed. [30,[32][33][34][35][36] This effect has been used to neglect free carriers in most simulation studies dealing with the piezoelectric response of semiconducting nanowirebased devices. A few papers have accounted for free carriers, although without account for SFLP.…”

mentioning

confidence: 99%

“…This effect commonly exists at the surface of III-V and II-VI semiconductor compounds. [29][30][31] At the surface of n-type ZnO NWs, oxygen molecules get negatively charged by capturing the free electrons from NW core. This forms a low-conductivity depletion layer near the surface, where the screening of piezoelectric potential by free carriers effect is suppressed.…”

mentioning

confidence: 99%

Unveiling the Influence of Surface Fermi Level Pinning on the Piezoelectric Response of Semiconducting Nanowires

Tao

Mouis

Ardila

2017

Adv Elect Materials

View full text Add to dashboard Cite

environment ever since they were first demonstrated. [4] Experimentally, it has been proved that ZnO NW based piezoelectric devices can generate a potential of a few volts. [15] This can be retrieved theoretically as long as there are no free carriers. However, experimentally prepared ZnO NWs are spontaneously n-type doped by impurities during their synthesis [16,17] and in such a case, screening by free carriers is expected to reduce drastically the piezoelectric response. There remain many such contradictions between experimental results and the present theoretical understanding of ZnO NW-based devices when realistic doping levels are considered. Chief among them are (1) decent and length-dependent performance of ZnO NWs, [18] while anticipations based on analytical and computational study showed that the output of NWs under compression were reduced to a few millivolts and presenting length-independent performance due to the screening effect; [19,20] (2) enhanced piezoelectric coefficients, [21] which were measured for ZnO NWs with diameter beyond the size effects anticipated by ab initio method; [22] and (3) dissymmetric piezoelectric response of bent nanogenerators (NGs) under tensile and compressive strain. [23] Relatively high potentials (>0.2 V) can be repeatedly obtained from NGs integrating long and large ZnO NWs [24][25][26][27] with presumably nonintentional doping. Increasing the doping concentration will reduce the generated piezopotential. [28] The nature of matrix material, as well as processing conditions, has been shown to play an important role. [24] (Table S1, Supporting Information).In this paper, we solve these contradictions by accounting for surface Fermi level pinning (SFLP). This effect commonly exists at the surface of III-V and II-VI semiconductor compounds. [29][30][31] At the surface of n-type ZnO NWs, oxygen molecules get negatively charged by capturing the free electrons from NW core. This forms a low-conductivity depletion layer near the surface, where the screening of piezoelectric potential by free carriers effect is suppressed. [30,[32][33][34][35][36] This effect has been used to neglect free carriers in most simulation studies dealing with the piezoelectric response of semiconducting nanowirebased devices. A few papers have accounted for free carriers, although without account for SFLP. [20,37] Here instead, full coupling between piezoelectric effect and semiconducting physics, including free carriers and SFLP, was considered.ZnO nanowires (NWs) are excellent candidates for the integration of energy harvesters, mechanical sensors, piezotronic and piezophototronic devices. However, ZnO NWs are usually nonintentionally n-doped during their growth. Thus, it can be expected theoretically that their piezoelectric response be degraded and mostly geometry-independent as a result of strong screening effects by free carriers, while experimentally many NW-based piezoelectric transducers demonstrate quite reasonable performance. In this paper, this apparent contradiction is explained by...

show abstract

“…The interfaces form the device, and the type of these interfaces (e.g. metal/metal, metal/semiconductor, or semiconductor junctions) along with related phenomena (Schottky barrier vs. ohmic contacts) define, together with the stability and the properties of the active layers, [1,2] the electronic characteristics, the performance, and the lifetime of a device. Although organic/metal interfaces have been the focus of nearly two decades of investigations, [3][4][5][6][7] very recently the interest in this type of interface has enjoyed a renaissance with the flourishing of a body of work focused mainly on the interfaces between chemisorbed organic molecules and metals.…”

mentioning

confidence: 99%

Fingerprint of Fractional Charge Transfer at the Metal/Organic Interface

Savu¹,

Biddau

Pardini

et al. 2015

J. Phys. Chem. C

View full text Add to dashboard Cite

Although physisorption is a widely occurring mechanism of bonding at the organic/metal interface, contradictory interpretations of this phenomenon are often reported. Photoemission and X-ray absorption spectroscopy investigations of nanorods of a substituted pentacene, 2,3,9,10-tetrafluoropentacene, deposited on gold single crystals reveal to be fundamental to identify the bonding mechanisms. We find fingerprints of a fractional charge transfer from the clean metal substrate to the physisorbed molecules. This phenomenon is unambiguously recognizable by a non-rigid shift of the core-level main lines while the occupied states at the interface stay mostly unperturbed, and the unoccupied states experience pronounced changes.The experimental results are corroborated by first-principles calculations.

show abstract

Solid Surfaces, Interfaces and Thin Films

Cited by 258 publications

References 0 publications

Local aspects of hydrogen-induced metallization of theZnO(101¯0)surface

Local aspects of hydrogen-induced metallization of theZnO(101¯0)surface

Unveiling the Influence of Surface Fermi Level Pinning on the Piezoelectric Response of Semiconducting Nanowires

Fingerprint of Fractional Charge Transfer at the Metal/Organic Interface

Contact Info

Product

Resources

About