Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New algorithm calculates average distance travelled by low-speed electrons

12.09.2014

Japanese researchers have achieved high accuracy in the measurement and analysis of nanosurface materials.

A research team consisting of postdoctoral researcher Da Bo, former postdoctoral researcher Hiroshi Shinotsuka, group leader Hideki Yoshikawa and special researcher Shigeo Tanuma, Surface Chemical Analysis Group, Nano Characterization Unit, NIMS (Sukekatsu Ushioda, president); and professor Ding Zejun, University of Science and Technology of China, has developed a theoretical algorithm to accurately calculate the average distance traveled by low-energy/low-speed electrons without any energy loss that are sensitive to the surface structures of materials through which they travel while retaining their energy information.


Inelastic mean free path (IMFP) of copper in relation to electron energy. Theoretical prediction using conventional algorithm (red band), theoretical prediction using newly developed algorithm (red solid line), and experimental data with improved accuracy.

Copyright : National Institute for Materials Science (NIMS)

This information on the average traveling distance is vital in terms of measuring the amount of electrons released from materials and gaining information about the depth at which surface analysis is conducted.

The nanometre-scale surface layers and interface layers influence the properties of various materials such as catalysts, batteries, semiconductors, sensors and anticorrosion materials. It is imperative to identify the amount of elements present and chemical bonding state in these layers in terms of improving the performance of functional materials and developing new materials.

And to achieve this, it is essential to accurately analyze and measure electrons (bonding electrons) that indicate the state of elements present in the surface and interface layers. This procedure involves measurement of bonding electron energy extracted from materials due to external stimuli applied to them in such forms as X-rays and electrons, and of the intensity distribution of that energy. During this process, it is critical to identify the depth from the surface at which these measurements were taken.

The range of the measurement depth can be determined by measuring a physical quantity called the inelastic mean free path (IMFP), which defines how far an electron can travel in a material while retaining its original energy level in a statistical sense. Experimental and theoretical attempts to quantify IMFP have been pursued globally since the 1970s. However, since it is difficult to take measurements on low-speed electrons that are sensitive to the surface structure (especially at 200eV or below), this quantification had been an issue for a long time.

In theory, accurate calculation of IMFP in a material is feasible provided that the energy loss function of that material is fully known. The energy loss function represents the level of interaction between the material and electromagnetic waves, and is expressed in terms of the change in the amount of energy lost from electrons and the change in momentum due to corresponding scattering events occurring in the material.

The conventional model function (so-called optical energy loss function) only enabled calculating a partial energy loss function under limited conditions assuming zero-momentum, however, lacking of the accompanied changing in momentum as electrons lose energy. As such, this is an incomplete energy loss function in view of obtaining IMFP. The conventional function was particularly problematic when that or similar functions were applied to low-speed electrons that are sensitive to the surface structure.

To overcome this problem, we described the optical energy loss function in terms of a composite function resulting from combining many functions, and also used a new model function that accurately expresses the change in momentum. With this method, we succeeded in determining a nearly complete energy loss function.

This calculation method enabled us to more accurately perform theoretical prediction of IMFP compared to the experimental value, which was obtained by applying spectrometry (extended X‐ray absorption fine structure spectrometry) to low-speed electrons of Copper and molybdenum at the high-brilliant synchrotron radiation facility, and to explain the relationship between energy measurement and the types of materials. Through this endeavor, we found a hint to solve this long-lasting problem.

Based on this research, more accurate quantification of elements and analysis of chemical bonding states have become feasible in the several atom thick surface layer of materials using electrons. The results of this study have been published in Physical Review Letters Vol.113 (2014) 063201. DOI: 10.1103/PhysRevLett.113.063201.

Associated links

Mikiko Tanifuji | Research SEA News
Further information:
http://www.researchsea.com

More articles from Materials Sciences:

nachricht Engineers develop smart material that changes stiffness when twisted or bent
15.02.2018 | Iowa State University

nachricht Breaking local symmetry: Why water freezes but silica forms a glass
14.02.2018 | Institute of Industrial Science, The University of Tokyo

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

Im Focus: Autonomous 3D scanner supports individual manufacturing processes

Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).

Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Fingerprints of quantum entanglement

16.02.2018 | Information Technology

'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers

16.02.2018 | Health and Medicine

Hubble sees Neptune's mysterious shrinking storm

16.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>