A5029106264- Chalcogenide Semiconductor Thin Films
- Quantum Dots Synthesis And Properties
- Advanced Semiconductor Detectors and Materials
- Semiconductor Quantum Structures and Devices
- ZnO doping and properties
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Ga2O3 and related materials
- GaN-based semiconductor devices and materials
- Copper-based nanomaterials and applications
- Gas Sensing Nanomaterials and Sensors
- Spectroscopy and Quantum Chemical Studies
- Nanowire Synthesis and Applications
- Laser-Matter Interactions and Applications
- Nonlinear Optical Materials Studies
- Inorganic Chemistry and Materials
- Quantum optics and atomic interactions
- Laser Material Processing Techniques
- Electronic and Structural Properties of Oxides
- Perovskite Materials and Applications
- Semiconductor materials and interfaces
- Thin-Film Transistor Technologies
- Laser-induced spectroscopy and plasma
- Strong Light-Matter Interactions
- Conducting polymers and applications
Technische Universität Braunschweig
2016-2025
University of Bayreuth
2019
University of Bremen
2007-2016
University of Bath
2013
University of Bristol
2013
University of Freiburg
2012
Harvard University
2007-2011
Harvard University Press
2009
Georgi Nadjakov Institute of Solid State Physics
2008
University of Göttingen
2008
We report the influence of an Al(2)O(3) shell on photoluminescence emission ZnO nanowires. At room temperature, spectrum core-shell nanowires shows a strong reduction relative intensity green defect with respect to near-band-edge emission. 5 K increase surface exciton band donor-bound is observed. Annealing at 500 °C does not luminescence K. propose model explaining spectral changes.
We use tapered silica fibers to inject laser light into ZnO nanowires with diameters around 250 nm study their waveguiding properties. find that high-order waveguide modes are frequently excited and carry significant intensity at the wire surface. Numerical simulations reproduce experimental observations indicate a coupling efficiency between of 50%. Experimentally, we an emission angle from about 90°, which is in agreement simulations.
Production of high-aspect-ratio silicon (Si) nanowire-based anode for lithium ion batteries is challenging particularly in terms controlling wire property and geometry to improve the battery performance. This report demonstrates tunable optimization inductively coupled plasma reactive etching (ICP-RIE) at cryogenic temperature fabricate vertically-aligned nanowire array anodes with high verticality, controllable morphology, good homogeneity. Three different materials [i.e., photoresist,...
Room-temperature near-band-edge photoluminescence of ZnO is composed contributions from free-exciton recombination and its longitudinal-optical phonon replica. By tracking the nanowires 4K up to room temperature, authors show that relative these emission lines a strong variation for samples grown under different conditions. The varying coupling strengths excitons phonons thus lead significant shift energy position room-temperature photoluminescence. They verify this not caused by laser...
The highly hydrated ionic liquid tetrabutylammonium hydroxide (TBAH) is an efficient precursor (ILP) for the fabrication of zinc oxide mesocrystals. Upon reaction TBAH with acetate, individual nanometer-sized ZnO building blocks assemble into correlated mesocrystals are up to ca. 10 µm in length and larger crystals have a channel running along long crystal axis.
We report on low temperature photoluminescence studies of ZnO nanowires embedded in different polymers. Comparing the spectra as-grown and nanowires, we find a decrease deep-level emission an increase near band-edge after embedding process. The is dominated by surface exciton band. observed effects are independent selected polymer. scales with balling abilities propose model to explain spectral changes.
The authors study the microscopic origin of electroluminescence from zinc oxide (ZnO) nanowire light-emitting diodes (LEDs) fabricated on a heavily doped p-type silicon (p-Si) substrate. By comparing low-temperature photoluminescence and single LED, bound- free-exciton related recombination processes, together with their longitudinal-optical phonon replicas, can be identified as both photoluminescence.
We develop ZnO/p-Si photodetectors by atomic layer deposition (ALD) of ZnO thin films on laser-microstructured silicon and we investigate their electrical optical behavior, demonstrating high sensitivity broadband operation. Microstructured p-type was obtained ns-laser irradiation in SF6 gas, which results the formation quasi-ordered uniform microspikes surface. The irradiated contains sulfur impurities, extend its absorbance to near infrared. A film conformally deposited microstructured...
We report on systematic investigations of the dynamics surface-excitonic (SX) near-band-edge photoluminescence ZnO nanowires observed at $\ensuremath{\approx}3.365\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The temporal evolution SX emission vapor-phase grown with diameters $d=40--130\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ is studied as a function spectral position, temperature, and excitation intensity. A phenomenological rate-equation model developed discussed which able to describe...
The structural, electrical, and optical properties of zinc oxide nanowire arrays electrodeposited from the reduction molecular oxygen in aqueous solutions containing chloride potassium are studied as a function concentration. concentration is varied wide range (from 5 × 10−5 to 3.4 M). evolution lattice parameters suggests formation interstitials, especially for [KCl] > 1 M. donor density deposited nanowires, which was determined electrochemical impedance spectroscopy (EIS), varies between 7...
We present a method which can be used for the mass-fabrication of nanowire photonic and electronic devices based on spin-on glass technology photolithographic definition independent electrical contacts to top bottom nanowire. This allows fabrication in reliable, fast, low cost way, it applied nanowires with arbitrary cross section doping type (p n). demonstrate this technique by fabricating single-nanowire p-Si(substrate)−n-ZnO(nanowire) heterojunction diodes, show good rectification...
Successful doping and excellent optical activation of Eu3+ ions in ZnO nanowires were achieved by ion implantation. We identified assigned the origin intra-4f luminescence first-principles calculations to Eu–Oi complexes, which are formed during nonequilibrium implantation process subsequent annealing at 700 °C air. Our targeted defect engineering resulted intense intrashell single ZnO:Eu dominating photoluminescence spectrum even room temperature. The high intensity enabled us study detail,...
Abstract The integration of gallium nitride (GaN) nanowire light-emitting diodes (nanoLEDs) on flexible substrates offers opportunities for applications beyond rigid solid-state lighting (e.g., wearable optoelectronics and bendable inorganic displays). Here, we report a fast physical transfer route based femtosecond laser lift-off ( fs -LLO) to realize wafer-scale top–down GaN nanoLED arrays unconventional platforms. Combined with photolithography hybrid etching processes, successfully...
Abstract An isotype heterojunction n + ‐ZnO/n‐Si photodetector is developed, showing adjustable wavelength‐selective operation at self‐powered conditions. Without an external bias voltage, the device can operate either as a broadband UV–vis–NIR or NIR‐only photodetector, depending on relative carrier concentrations of ZnO and silicon. In addition, be tuned to NIR by application regardless concentrations. At negative bias, it demonstrates photodetection, while positive photodetection....
We report on the photoluminescence properties of ZnO nanowires treated with a mild Ar plasma. The exhibited stable and strong enhancement near-band-edge emission quenching deep level emission. low temperature PL revealed hydrogen donor–bound-exciton line in plasma-treated samples indicating unintentional incorporation during plasma treatment. To confirm results, was implanted into ion energy 600 eV different fluences. observed result can be related to passivation centers by hydrogen....
Microfabrication via two-photon absorption polymerization is a technique to design complex microstructures in simple and fast way. The applications of such structures range from mechanics photonics biology, depending on the dopant material its specific properties. In this paper, we use fabricate optically active containing conductive luminescent polymer poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV). We verify that MEH-PPV retains optical activity distributed throughout...
Abstract The combination of inorganic semiconductors with organic thin films promises new strategies for the realization complex hybrid optoelectronic devices. Oxidative chemical vapor deposition (oCVD) conductive polymers offers a flexible and scalable path towards high-quality three-dimensional inorganic/organic structures. Here, hole-conductive poly(3,4-ethylenedioxythiophene) (PEDOT) grown by oxidative is used to fabricate transparent conformal wrap-around p-type contacts on microLEDs...
Single crystal ZnO wurtzite nanowires grown along the c-axis with diameters down to 4 nm were synthesized by a catalytic vapor transport technique. Photoluminescence spectra of these wires indicate blue shift free exciton 19 meV due confinement. This result was obtained analyzing line shape blue-shifted LO phonon replica exciton. In addition, surface-related excitonic luminescence feature centered at 3.366 eV observed strongly elevated thermal activation energy.
We present a broadband (460 - 980 nm) analysis of the nonlinear absorption processes in bulk ZnO, large-bandgap material with potential blue-to-UV photonic device applications. Using an optical parametric amplifier we generated tunable 1-kHz repetition rate laser pulses and employed Z-scan technique to investigate spectrum ZnO. For excitation wavelengths below 500 nm, observed reverse saturable due one-photon sample, agreeing rate-equation modeling. Two- three-photon were from 540 nm. also...
We investigated the photoluminescence properties of ZnO nanowires coated with Au, Ag, and Pt nanoparticles deposited by dc sputtering. A strong enhancement near-band-edge emission was observed in all metal-coated samples but also if were treated Ar plasma without any nanoparticle deposition. High-resolution spectroscopy revealed hydrogen-donor-bound-exciton indicating unintentional hydrogen incorporation. shorter decay time cases. The results indicate that incorporation plays a dominant role...
Zinc oxide nanorod structures constitute a promising concept to improve light management in photovoltaic devices. This paper reports on the antireflective properties of zinc arrays hydrogenated amorphous silicon thin‐film solar cells. Arrays with different structure sizes, grown by electrochemical deposition aluminum doped seed layers thicknesses (400 nm, 800 1200 nm), are compared. The results show reduction average weighted cell reflectivity up 6.1%, as well enhanced quantum efficiencies...