Nav: Home

Russian scientists found excitons in nickel oxide for the first time

January 12, 2018

Russian scientists from Ural Federal University (UrFU) together with their colleagues from Institute of Metal Physics of the Ural Department of Russian Academy of Sciences studied fundamental characteristics of nickel oxide nanocrystals and found excitons on the light absorption edge for the first time. An exciton is an electron-hole pair bound with electrostatic coupling that migrates in a crystal and transmits energy within it. The presence of an exciton in the studied area allows for detailed research of edge parameters in permitted energy bands. This may be useful for the development of new generation optoelectronic devices. The results of the study were published in Physica B: Physics of Condensed Matter journal.

It is impossible to imagine modern world without electricity. By the ability to conduct electricity all solid objects, liquids and (under certain circumstances) gases are divided into conductors and dielectrics. The former conduct electricity, and the latter, respectively, do not. A group between them is called semiconductors. In their case conductivity occurs due to the movement of charged electrons and holes within the crystal. They are found in systems with impurities that can either release or receive electrons, as well as after irradiation with high-energy light.

"In the physics of semiconductors, there is a notion of fundamental adsorption edge that indicated the edge-level energy of light adsorption. It corresponds to the energy gap - the area of energies an electron has to pass in the course of movement under the influence of light from the valence band (where it is usually located) to the conductivity band. A positively charged empty space that occurs at this place is called a hole. Its electrostatic (Coulombic) interaction with the electron in the conduction band causes the formation of an electron-hole pair, or and exciton. In the optic spectrum it can be seen as a narrow line a little below the fundamental adsorption edge. Notably, an exciton does not participate in electrical conductivity, but transfers the absorbed energy" comments Anatoly Zatsepin, a co-author of the article, and the head of a scientific lab at UrFU.

Excitons bond energy is too small, so the temperature should be low in order to register them. After being irradiated with the light of the short wavelength range, such as UV radiation, an electron-hole pair collapses as the excitation is too high. Excessive energy is released also in the form of radiation, and its spectrum may be registered. This is how excitons were found in nanosized (one nanometer is 10-9 m) crystals of nickel oxide. It should be pointed out that a system like this is highly correlated, i.e. the interaction between its parts is very strong that determines the occurrence of such interesting phenomena. The research team studied fundamental adsorption edge at low temperatures and found out lines in which intensity decreased when the temperature was growing. These facts as well as the values of energies indicate their exciton nature. Scientists also studied fundamental characteristics of magnesium oxide nanocrystals with small admixtures of nickel. In this case excitons were formed upon the transition of the electron (and therefore the negative charge) from the valence band of the main component to the admixture area. The hole was bound with an electrostatic field generated by the electron. The detection of excitons is a sensitive tool for studying the complicated structure of the border area between the valence band and the conductivity band in semiconductors.

"We first found excitons with charge transfer at the boundary of fundamental adsorption in nickel oxide and at the impurity adsorption edge in magnesium oxide. These results may be of interest to specialists in theoretical physics who study the band structure of oxides with strong correlations. NiO has been considered as prototype of such oxides for a long time, and many calculation schemes have been tested using this object. The results may also be relevant for the development of new optoelectronic devices," concludes Anatoly Zatsepin.

The experimental work was accomplished in the new department of UrFU - the Physics of Functional Materials in Micro- and Optoelectronics lab of Institute of Physics and Technology, UrFU.

Ural Federal University

Related Electricity Articles:

Microbial fuel cell converts methane to electricity
Transporting methane from gas wellheads to market provides multiple opportunities for this greenhouse gas to leak into the atmosphere.
Exploring the conversion of heat to electricity in single molecules
Researchers at Osaka University investigated the influence of the geometry of single-molecule devices on their ability to produce electricity from heat.
Macrophages conduct electricity, help heart to beat
Macrophages have a previously unrecognized role in helping the mammalian heart beat in rhythm.
Buzzing the brain with electricity can boost working memory
Scientists have uncovered a method for improving short-term working memory, by stimulating the brain with electricity to synchronize brain waves.
Environmentally friendly, almost electricity-free solar cooling
Demand and the need for cooling are growing as the effects of climate change intensify.
1 in 5 residents overuses electricity at neighbors' expense
Household electricity use falls by more than 30 percent when residents are obliged to pay for their own personal consumption.
New approach for matching production and consumption of renewable electricity
VTT Technical Research Centre of Finland is coordinating the BALANCE project, which brings together leading European research institutes in the field of electrochemical conversion.
Electricity costs: A new way they'll surge in a warming world
Climate change is likely to increase US electricity costs over the next century by billions of dollars more than economists previously forecast, according to a new study involving a University of Michigan researcher.
Material can turn sunlight, heat and movement into electricity -- all at once
Many forms of energy surround you: sunlight, the heat in your room and even your own movements.
For this metal, electricity flows, but not the heat
Berkeley scientists have discovered that electrons in vanadium dioxide can conduct electricity without conducting heat, an exotic property in an unconventional material.

Related Electricity Reading:

Basic Electricity (Dover Books on Electrical Engineering)
by Bureau of Naval Personnel (Author)

This expanded and revised U.S. Navy training course text provides thorough coverage of the basic theory of electricity and its applications. It is unquestionably the best book of its kind for either broad or more limited studies of electrical fundamentals.
It is divided into 21 chapters and an extensive section of appendixes. Chapters cover safety, fundamental concepts of electricity, batteries, series direct-current circuits, network analysis of direct-current circuits, electrical conductors and wiring techniques, electromagnetism and magnetic circuits, introduction to... View Details

Delmar's Standard Textbook of Electricity
by Stephen Herman (Author)

Note: This ISBN is a standalone, Hardbound book. There is no access card with this ISBN. Packed with high-quality photos and illustrations, DELMAR'S STANDARD TEXTBOOK OF ELECTRICITY, 6e combines comprehensive coverage of basic electrical theory with practical "how to" information that prepares readers for real-world practice. The text covers all aspects of basic theory principles new learners need to know. Its clear presentation uses schematics and large illustrations to bring concepts to life, while examples throughout demonstrate how to do common tasks electricians perform. The Sixth... View Details

Schaum's Outline of Basic Electricity, Second Edition (Schaum's Outlines)
by Milton Gussow (Author)

Confused by basic electricity concepts? Problem solved

Schaum's Outline of Basic Electricity covers the fundamentals of electricity and electric circuits. Written as a complement to vocational and technical courses, the book reviews digital and computer technology and the more advanced level of expertise required of technicians in these fields. Chapters focus on particular subjects as they are related to electric circuits, so you can target specific areas or tackle the subject as a whole. You will also learn how to solve circuit values in more complex series and... View Details

Teach Yourself Electricity and Electronics, Sixth Edition
by Stan Gibilisco (Author), Simon Monk (Author)

Learn electricity and electronics fundamentals and applications―all without taking a formal course


This fully updated guide offers practical, easy-to-follow instruction on electricity and electronics. Written by a pair of experienced instructors, Teach Yourself Electricity and Electronics, Sixth Edition, features plain language explanations and step-by-step lessons that make it easy to understand the material quickly. Throughout,... View Details

Electricity Demystified, Second Edition
by Stan Gibilisco (Author)

Add some SPARK to your study of ELECTRICITY

Having trouble understanding the fundamentals of electricity? Problem solved! Electricity Demystified, Second Edition, makes it shockingly easy to learn the basic concepts.

Written in a step-by-step format, this practical guide begins by covering direct current (DC), voltage, resistance, circuits, cells, and batteries. The book goes on to discuss alternating current (AC), power supplies, wire, and cable. Magnetism and electromagnetic effects are also addressed. Detailed examples and concise explanations make it easy to understand... View Details

Basic Electricity
by U. S. Naval Personnel (Author), The Editors of REA (Author), Engineering Study Guides (Author)

The material in this book was prepared for electrical training courses. It is a practical manual that enables even the beginner to grasp the various topics quickly and thoroughly. The book is one of a kind in that it teaches the concepts of basic electricity in a way that's clear, to-the-point, and very easy to understand. It forms an excellent foundation for those who wish to proceed from the basics to more advanced topics. Numerous illustrations are included to simplify learning both theories and their applications. Direct-current and alternating-current devices and circuits are explained... View Details

DK Eyewitness Books: Electricity
by Steve Parker (Author)

The most trusted nonfiction series on the market, Eyewitness Books provide an in-depth, comprehensive look at their subjects with a unique integration of words and pictures.

Eyewitness: Electricity presents the story of electricity — from the earliest discoveries to the technologies of today — explaining how our eyes receive light rays and turn them into electrical signals, how the chemicals in batteries work, how the invention of electric motors allowed for the creation of household appliances, what happens when you tune in the radio, and more.

View Details

The Magic School Bus And The Electric Field Trip
by Joanna Cole (Author), Bruce Degan (Author), Bruce Degen (Illustrator)

To celebrate its 20th anniversary, Scholastic is re-releasing the ten original Magic School Bus titles in paperback. With updated scientific information, the bestselling science series ever is back! Small enough to squeeze through power lines, Ms. Frizzle's class learns how electric current travels through the town, lights up a light bulb, heats up a toaster, and runs an electric motor. Fans of the Magic School Bus won't be left behind by this simple and informative introduction to the generation and distribution of electricity. View Details

Oscar and the Bird: A Book about Electricity (Start with Science)
by Geoff Waring (Author), Geoff Waring (Illustrator)

Two new Start with Science books introduce kids to core science concepts through engaging stories, fresh illustrations, and supplemental activities. (Age 4 and up)

When Oscar the kitten finds a tractor in a field and accidentally turns on the windshield wipers, he is full of questions about electricity. Luckily, Bird knows the answers! With the help of his friend, Oscar finds out how electricity is made and stored, which machines need electricity to work — and why we always need to be careful around wires, batteries, plugs, and sockets.
Back matter includes an index and... View Details

Electricity and Magnetism
by Edward M. Purcell (Author), David J. Morin (Author)

For 50 years, Edward M. Purcell's classic textbook has introduced students to the world of electricity and magnetism. The third edition has been brought up to date and is now in SI units. It features hundreds of new examples, problems, and figures, and contains discussions of real-life applications. The textbook covers all the standard introductory topics, such as electrostatics, magnetism, circuits, electromagnetic waves, and electric and magnetic fields in matter. Taking a nontraditional approach, magnetism is derived as a relativistic effect. Mathematical concepts are introduced in... View Details

Best Science Podcasts 2018

We have hand picked the best science podcasts for 2018. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

The Consequences Of Racism
What does it mean to be judged before you walk through the door? What are the consequences? This week, TED speakers delve into the ways racism impacts our lives, from education, to health, to safety. Guests include poet and writer Clint Smith, writer and activist Miriam Zoila Pérez, educator Dena Simmons, and former prosecutor Adam Foss.
Now Playing: Science for the People

#465 How The Nose Knows
We've all got a nose but how does it work? Why do we like some smells and not others, and why can we all agree that some smells are good and some smells are bad, while others are dependant on personal or cultural preferences? We speak with Asifa Majid, Professor of Language, Communication and Cultural Cognition at Radboud University, about the intersection of culture, language, and smell. And we level up on our olfactory neuroscience with University of Pennsylvania Professor Jay Gottfried.