Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > An old dream has been fulfilled: Zinc oxide as semiconductor: RUB scientists identify hydrogen as disturbance factor Theoretical predictions have been

Research scientists at the Ruhr-University in Bochum were able to show that hydrogen atoms always result in n-doping. They could reversibly dope zinc oxide substrates using hydrogen and then eliminate the hydrogen by heating.
Research scientists at the Ruhr-University in Bochum were able to show that hydrogen atoms always result in n-doping. They could reversibly dope zinc oxide substrates using hydrogen and then eliminate the hydrogen by heating.

Abstract:
Zinc oxide is a "jack of all trades" - thousands of tons thereof are produced all over the world every year. Its fields of utilization range from food additive to sun screening agents. It is even significant as semiconductor, although the great breakthrough in this field is yet to come. Perfect doping is not yet possible. A team of chemical scientists at the Ruhr-University in Bochum, working under the auspices of Prof. Christof Wöll, is a step closer to unveiling the reason. They were experimentally able to provide evidence that hydrogen atoms disturb the process. Controlled concentration of hydrogen atoms during the production of intrinsic zinc oxide is thus the key to the routine use of ZnO as semiconductor. The scientists have documented their results in the journal Physical Review Letters.

An old dream has been fulfilled: Zinc oxide as semiconductor: RUB scientists identify hydrogen as disturbance factor Theoretical predictions have been

Bochum, Germany | Posted on December 6th, 2008

Doping activates the semiconductor
Doping, i.e. the insertion of specific foreign atoms into the crystal lattice of a solid, is the most important factor during the production of semiconductor devices. These foreign atoms either release an electron (n-doping), or absorb an electron, thus creating a "hole" in the solid (p-doping). These mobile electrons or holes then bring about the electric conductivity of the otherwise isolated semiconductor, i.e. doping initiates "action" in the semiconductor. This standard process in the manufacturing of conventional semiconductors e.g. silicon or germanium has however been problematic for zinc oxide to date. In particular, it has been difficult to achieve p-doping, which made it impossible to construct semiconductor devices such as transistors or light emitting diodes (LEDs). Such devices require a pn-transition, a junction between the p-doped and the n-doped zones. Thus, in the field of semiconductors, zinc oxide is at present only used for a few special applications.

Hydrogen is always present
There has been a significant improvement in the production of intrinsic zinc oxide during the past few years. Blue LEDs made of zinc oxide have only been presented recently. There are, however, still numerous problems concerning doping. Research scientists at the Ruhr-University in Bochum have been able to identify a significant obstacle in the production of intrinsic zinc oxide. During experiments, which had actually been motivated by an interest in the catalytic properties of ZnO, they were able to show that hydrogen atoms always result in n-doping. They could reversibly dope zinc oxide substrates using hydrogen and then eliminate the hydrogen by heating. The scientists were thus able to verify theoretical predictions made in 2000. They used a special technique for measurements at diverse temperatures to verify the corresponding charge carrier concentrations. A sufficiently high density of these charge carriers is essential for the proper functioning of electronic devices. Hydrogen impurities are almost impossible to avoid during the production process, thus preventing the targeted p-doping. The electrons released from the H atoms to the ZnO immediately fill the holes caused by the p-doping. High purity, in particular a hydrogen-free environment, is thus a decisive factor for the production of intrinsic zinc oxide.

Controversy is history
The research team was thus also able to resolve a scientific controversy: to date it has often been postulated that the doping problems are caused by imperfections in the zinc oxide crystal lattice, by additional Zn atoms or oxygen defects. The results obtained in Bochum are a basis for the production of higher performance ZnO-based electronic circuits. Currently the scientists are doing intensive research to attain p-doping with an intrinsic, i.e. hydrogen-free, zinc oxide substrate by incorporating appropriate foreign atoms.

Technology actually intended for another purpose
The technology used, a special version of electron spectroscopy, is normally used for another purpose, namely for the investigation of chemical processes on the surfaces of zinc oxides. Such phenomena have been investigated at the Ruhr-University in Bochum for many years within the frameworks of SFB 558 (Focus Research Centre - Metal-Substrate Interactions in Heterogeneous Catalysis) due to the significance of zinc oxide for heterogeneous catalysis, particularly for the synthesis of methanol.

Title
H. Qiu, B. Meyer, Y. Wang, Ch. Wöll: Ionization energies of shallow donor states in ZnO created by reversible formation and depletion of H interstitials. In: Physical Review Letters 101, 236401 (2008), DOI: 10.1103/PhysRevLett.101.236401

####

For more information, please click here

Contacts:
Prof. Christof Wöll
Department of Physical Chemistry I
Ruhr-University Bochum
D-44780 Bochum, Germany
Tel: +49 (0) 234/32-25529
Fax: +49 (0) 234/32-14182

Copyright © Ruhr University Bochum

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

First Observation of Electronic Structure in Ag-Rh Alloy Nanoparticles Having Hydrogen Absorbing: Storage Property –Attempting to solve the mystery of why Ag-Rh alloy nanoparticles have a similar property to Pd– October 30th, 2014

Iranians Present Model to Predict Photocatalytic Process in Removal of Pollutants October 30th, 2014

Production of Biocompatible Polymers in Iran October 30th, 2014

Amorphous Coordination Polymer Particles as alternative to classical nanoplatforms for nanomedicine October 30th, 2014

Chip Technology

Sussex physicists find simple solution for quantum technology challenge October 28th, 2014

Watching the hidden life of materials: Ultrafast electron diffraction experiments open a new window on the microscopic world October 27th, 2014

Breakthrough in molecular electronics paves the way for DNA-based computer circuits in the future: DNA-based programmable circuits could be more sophisticated, cheaper and simpler to make October 27th, 2014

QuantumWise guides the semiconductor industry towards the atomic scale October 24th, 2014

Discoveries

First Observation of Electronic Structure in Ag-Rh Alloy Nanoparticles Having Hydrogen Absorbing: Storage Property –Attempting to solve the mystery of why Ag-Rh alloy nanoparticles have a similar property to Pd– October 30th, 2014

Iranians Present Model to Predict Photocatalytic Process in Removal of Pollutants October 30th, 2014

Production of Biocompatible Polymers in Iran October 30th, 2014

Amorphous Coordination Polymer Particles as alternative to classical nanoplatforms for nanomedicine October 30th, 2014

Announcements

First Observation of Electronic Structure in Ag-Rh Alloy Nanoparticles Having Hydrogen Absorbing: Storage Property –Attempting to solve the mystery of why Ag-Rh alloy nanoparticles have a similar property to Pd– October 30th, 2014

Iranians Present Model to Predict Photocatalytic Process in Removal of Pollutants October 30th, 2014

Production of Biocompatible Polymers in Iran October 30th, 2014

Amorphous Coordination Polymer Particles as alternative to classical nanoplatforms for nanomedicine October 30th, 2014

NanoNews-Digest
The latest news from around the world, FREE





  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More














ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE