Production of native donors in ZnO by annealing at high temperature in Zn vapor

Halliburton, L. E.; Giles, N. C.; Garces, N. Y.; Luo, Ming; Xu, Chunchuan; Bai, Lihai; Boatner, L. A.

doi:10.1063/1.2117630

Cited by 162 publications

(130 citation statements)

References 34 publications

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“…Recently, it has been confirmed by Selim et al 32 and Halliburton et al 33 that red colouration in ZnO is due to V O s. This is further evident from the fact that the red coloured ZnO becomes colourless transparent by annealing in oxygen atmosphere 32,34 . In the present case, the white samples turns out orange and finally dark reddish brown (appears as black) with increase of irradiation fluence (Fig.…”

supporting

confidence: 56%

Interplay of defects in 1.2 MeV Ar irradiated ZnO

Chattopadhyay

Dutta

Jana

et al. 2010

Journal of Applied Physics

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Defect characterization in 1.2 MeV Ar8+ irradiated polycrystalline ZnO has been carried out by x-ray diffraction (XRD), scanning electron microscopy (SEM) along with electrical resistivity, and photoluminescence (PL) measurements at room temperature (RT). Interestingly, irradiation with the initial fluence (1×1015 ions/cm2) changes the color of the sample from white to orange while the highest irradiation fluence (5×1016 ions/cm2) makes it dark reddish brown that appears as black. XRD study reveals no significant change in the average grain size of the samples with irradiation fluence. Increase in surface roughness due to sputtering is clearly visible in SEM with highest fluence of irradiation. RT PL spectrum of the unirradiated sample shows intense ultraviolet (UV) emission (∼3.27 eV) and less prominent defect level emissions (2–3 eV). The overall emission is largely quenched due to initial irradiation fluence. Increasing the fluence of Ar beam further, UV emission is enhanced along with prominent defect level emissions. Remarkably, the resistivity of the irradiated sample with highest fluence is reduced by four orders of magnitude compared to that of the unirradiated sample. This is due to an increase in donor concentration as well as their mobility induced by high fluence of irradiation. Change in color in the irradiated samples indicates dominant presence of oxygen vacancies. It is now well known that oxygen vacancies are deep donors in ZnO. So oxygen vacancies, in principle, are not the source of conductivity in ZnO at RT. Simultaneous evolution of coloration and conductivity in ZnO, as is seen in this study, indicate that oxygen vacancies strongly influence the stability of shallow donors, presumably zinc interstitial related (highly mobile Zn interstitials also need to form defect pair/complex to be stable), which act as major source of carriers. Such a contention is in conformity with most recent theoretical calculations.

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confidence: 56%

Interplay of defects in 1.2 MeV Ar irradiated ZnO

Chattopadhyay

Dutta

Jana

et al. 2010

Journal of Applied Physics

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“…By design, the depleted region of the heterojunction (depletion width X = 0.646 µm) mainly extends within the p-Si (XSi = 0.637 µm), according to the impurity concentrations of the here used materials (Na = 1.355·10 15 cm -3 for p-Si) and assuming a typical value of Nd = 110 17 cm -3 for n-ZnO produced by this method. [15,16] Under these conditions, the theoretical Voc in an ideal heterojunction has been estimated to be Voc,theor,ideal = 479 mV/diode, which relates to the built-in potential formed between the ZnO conduction band and siliconi valence band under non-biased conditions (see supporting information). …”

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confidence: 99%

A Highly Selective and Self‐Powered Gas Sensor Via Organic Surface Functionalization of p‐Si/n‐ZnO Diodes

et al. 2014

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Low power consumption and reliable selectivity are the two main requirements for gas sensors to be applicable in mobile devices. [1] These technological platforms, e.g. smart phones or wireless sensor platforms will facilitate personalized detection of environmental and health conditions, and hence becoming the basis of the future core technology of ubiquitous sensing. Even today, health control as well as environmental monitoring is relying on immobile and complex detection systems with very limited availability in space and time. Recent works have shown promising concepts to realize selfpowered gas sensors that are capable of detecting gases without the need of external power sources to Submitted to 2 activate the sensor-gas interaction or to actively generate a read out signal. [2,3] These sensors drastically reduce power consumption compared to conventional semiconductor gas sensors and additionally reduce the required space for integration. All these attempts so far were based on purely nano structured inorganic metal oxide sensor materials that provide a good sensitivity towards different gases due to their high surface-to-volume ratio. However, due to their non-selective sensing mechanism based on oxygen vacancy-gas interactions, these purely inorganic sensors cannot accomplish a meaningful gas selectivity. [4,5] High selectivities towards single gas species have been recently reported via modifying the inorganic surface of nanostructured semiconductors with a defined organic functionality. [6][7][8][9] Theoretical simulations based on ab-initio density functional theory (DFT) for a system composed of SnO2 NWs modified with a defined self assembled monolayer (SAM) elucidated the reason for the high selectivity of such gas sensor: the energetic position of the SAM-gas frontier orbitals with respect to the NW Fermi level have been identified to be the crucial factor to ensure an efficient charge transfer upon gas-SAM binding interactions and thus to sense or discriminate a certain gas species. [7] The high flexibility of organic surface modifications in terms of functional groups as well as their sterical and electronic structure possibly might enable the targeted design of various specific gas sensors. However, all organic surface modified sensor systems so far are based on compact conductometric or field effect transistor (FET) sensor concepts that still require a remarkable amount of energy to generate a sensor signal (e.g. by applying a source-drain current). Up to date, none of the semiconductor based gas sensor systems could accomplish both, the selfpowered/low powered sensor operation and highly selective gas detection within a single and compact device.In this work, we present a semiconductor based gas sensor concept that combines the two substantial requirements of mobile gas sensing in a singular sensor device: self-powered operation combined with high gas selectivity. Beyond the combination of self-powered sensing and high selectivity, also a very high sensitivity could also been demonst...

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“…20 For some experiments, an oxidized surface was prepared by exposing the sample to activated oxygen from an atomic oxygen source (Oxford Applied Research Thermal Gas Cracker TC-50; oxygen pressure: 2.5 × 10 −7 mbar) for 30 minutes at a sample temperature of 300…”

Section: Surface Qualitymentioning

confidence: 99%

Bulk and surface characterization of In2O3(001) single crystals

et al. 2012

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A comprehensive bulk and surface investigation of high-quality In 2 O 3 (001) single crystals is reported. The transparent-yellow, cube-shaped single crystals were grown using the flux method. Inductively coupled plasma mass spectrometry (ICP-MS) reveals small residues of Pb, Mg, and Pt in the crystals. Four-point-probe measurements show a resistivity of 2.0 ± 0.5 × 10 5 cm, which translates into a carrier concentration of ≈10 12 cm −3 . The results from x-ray diffraction (XRD) measurements revise the lattice constant to 10.1150(5)Å from the previously accepted value of 10.117Å. Scanning tunneling microscopy (STM) images of a reduced (sputtered/annealed) and oxidized (exposure to atomic oxygen at 300• C) surface show a step height of 5Å, which indicates a preference for one type of surface termination. The surfaces stay flat without any evidence for macroscopic faceting under any of these preparation conditions. A combination of low-energy ion scattering (LEIS) and atomically resolved STM indicates an indium-terminated surface with small islands of 2.5Å height under reducing conditions, with a surface structure corresponding to a strongly distorted indium lattice. Scanning tunneling spectroscopy (STS) reveals a pronounced surface state at the Fermi level (E F ). Photoelectron spectroscopy (PES) shows additional, deep-lying band gap states, which can be removed by exposure of the surface to atomic oxygen. Oxidation also results in a shoulder at the O 1s core level at a higher binding energy, possibly indicative of a surface peroxide species. A downward band bending of 0.4 eV is observed for the reduced surface, while the band bending of the oxidized surface is of the order of 0.1 eV or less.

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Production of native donors in ZnO by annealing at high temperature in Zn vapor

Cited by 162 publications

References 34 publications

Interplay of defects in 1.2 MeV Ar irradiated ZnO

Interplay of defects in 1.2 MeV Ar irradiated ZnO

A Highly Selective and Self‐Powered Gas Sensor Via Organic Surface Functionalization of p‐Si/n‐ZnO Diodes

Bulk and surface characterization of In2O3(001) single crystals

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