Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Identification of Atomic Species at the Surface of Anatase Titanium Dioxide by Scanning Probe Microscopy

14.09.2015

A research team at Japan's National Institute for Materials Science (NIMS) successfully identified the atoms and common defects existing at the most stable surface of the anatase form of titanium dioxide by characterizing this material at the atomic scale with scanning probe microscopy.

The study contributes to formulate novel approaches for the development of photo-catalysts and solar energy conversion materials.


Simultaneous atomic-scale AFM (a) and STM (b) images of the (101) surface of anatase titanium dioxide. The parallelograms indicate the same surface area in (a) and (b). The positions of maximum signal (bright spots) in the AFM and STM images clearly differ. By using single water molecules as atomic markers and combining simultaneous AFM and STM measurements with first-principles calculations, the authors demonstrated that the AFM images the first atomic layer of oxygen atoms-pink spheres in the model of the anatase (101) surface depicted in (c)-and the STM images the titanium atoms at the third atomic layer-dark gray spheres in (c). Copyright : NIMS

The research team consisting of Oscar Custance and Tomoko Shimizu, group leader and senior scientist, respectively, at the Atomic Force Probe Group, NIMS, Daisuke Fujita and Keisuke Sagisaka, group leader and senior researcher, respectively, at the Surface Characterization Group, NIMS, and scientists at Charles University in the Czech Republic, Autonomous University of Madrid in Spain, and other organizations combined simultaneous atomic force microscopy (AFM) and scanning tunneling microscopy (STM) measurements with first-principles calculations for the unambiguous identification of the atomic species at the most stable surface of the anatase form of titanium dioxide (hereinafter referred to as anatase) and its most common defects.

In recent years, anatase has attracted considerable attention, because it has become a pivotal material in devices for photo-catalysis and for the conversion of solar energy to electricity. It is extremely challenging to grow large single crystals of anatase, and most of the applications of this material are in the form of nano crystals.

To enhance the catalytic reactivity of anatase and the efficiency of devices for solar energy conversion based on anatase, it is critical to gain in-depth understanding and control of the reactions taking place at the surface of this material down to the atomic level. Only a few research groups worldwide possess the technology to create proper test samples and to make in-situ atomic-level observations of anatase surfaces.

In this study, the research team used samples obtained from anatase natural single crystals extracted from naturally occurring anatase rocks. The team characterized the (101) surface of anatase at atomic level by means of simultaneous AFM and STM.

Using single water molecules as atomic markers, the team successfully identified the atomic species of this surface; result that was additionally confirmed by the comparison of simultaneous AFM and STM measurements with the outcomes of first-principles calculations.

In regular STM, in which an atomically sharp probe is scanned over the surface by keeping constant an electrical current flowing between them, it is difficult to stably image anatase surfaces as this material presents poor electrical conductivity over some of the atomic positions of the surface.

However, simultaneous operation of AFM and STM allowed imaging the surface with atomic resolution even within the materials band gap (a region where the flow of current between the probe and the surface is, in principle, prohibited). Here, the detection of inter-atomic forces between the last atom of the atomically sharp probe and the atoms of the surface by AFM was of crucial importance.

By regulating the probe-surface distance using AFM, it was possible to image the surface at atomic-scale while collecting STM data over both conductive and not conductive areas of the surface. By comparing simultaneous AFM and STM measurements with theoretical simulations, the team was not only able to discern which atomic species were contributing to the AFM and the STM images but also to identify the most common defects found at the surface.

In the future, based on the information gained from this study, the NIMS research team will conduct research on molecules of technologically relevance that adsorb on anatase and characterize these hybrid systems by using simultaneous AFM and STM. Their ultimate goal is to formulate novel approaches for the development of photo-catalysts and solar cell materials and devices.

This study was published under open access policy in the online version of Nature Communications on June 29, 2015.

Associated links
Original press release from NIMS

Mikiko Tanifuji | ResearchSea
Further information:
http://www.researchsea.com

Further reports about: AFM Materials Science Microscopy NIMS STM Titanium crystals material materials solar energy species

More articles from Materials Sciences:

nachricht Strange but true: Turning a material upside down can sometimes make it softer
20.10.2017 | Universitat Autonoma de Barcelona

nachricht Metallic nanoparticles will help to determine the percentage of volatile compounds
20.10.2017 | Lomonosov Moscow State University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>