Shaping the hilly landscapes of a semi-conductor nanoworld
A new study reveals how hexagonal-patterned, self-organised hill structures emerge in 2-D at the nanoscale due to redeposition following semi-conductor bombardment with low-energy ions
2015-07-31
(Press-News.org) Nanoscale worlds sometimes resemble macroscale roller-coaster style hills, placed at the tip of a series of hexagons. Surprisingly, these nanohills stem from the self-organisation of particles - the very particles that have been eroded and subsequently redeposited following the bombardment of semi-conductors with ion beams. Now, a new theoretical study constitutes the first exhaustive investigation of the redeposition effect on the evolution of the roughening and smoothing of two-dimensional surfaces bombarded by multiple ions. The results demonstrate that the redeposition can indeed act as stabilising factor during the creation of the hexagonally arranged dot patterns observed in experiments. These findings by Christian Diddens from the Eindhoven University of Technology, in the Netherlands, and Stefan Linz, from Munster University, Germany, have been published in a study published in EPJ B.
To calculate multiple simulations of redeposition within reasonable computation times, the authors have developed an elaborate new highly efficient algorithm that combines established erosion models with a redeposition model. The latter made it possible to approximate the entire microscopic redeposition dynamics as a function of the relative height and the local slope of a coarse-grained surface. This approach is also supplemented by a new numerical algorithm to calculate precisely how the matter lifted by the ion beams is subsequently redeposited.
This led to the realisation that eroded particles predominantly redeposit in the vicinity of the valleys, whereas almost no particles reattach at the hilltops. Overall, they found that the redeposition mechanism can contribute towards the formation of stable hexagonal patterns. They also confirmed that the aspect ratio of the well-ordered structures resulting from numerical simulation is comparable with experimental findings. This means that the reattachment of eroded particles can play an important role in the observed nanostructures formations. At the same, they comprehensively investigated the distribution of redepositing particles on patterned surfaces.
INFORMATION:
Reference:
C. Diddens and S. J. Linz (2015), Continuum modeling of particle redeposition during ion-beam erosion, Eur. Phys. J. B 88:190, DOI: 10.1140/epjb/e2015-60468-7
ELSE PRESS RELEASES FROM THIS DATE:
2015-07-31
Using ultracold atoms trapped in light crystals, scientists from the Ludwig-Maximilians-Universitaet (LMU) in Munich, the Max Planck Institute of Quantum Optics, and the Weizmann Institute observe a novel state of matter that never thermalizes.
What happens if one mixes cold and hot water? After some initial dynamics, one is left with lukewarm water--the system has thermalized to a new thermal equilibrium. This is true not only when we pour cold milk into our hot coffee, but it is also what happens for almost all interacting systems we know in nature: in the long run ...
2015-07-31
Several rare upland bird species are being put at risk together with other ecosystem functions by the effects of climate change on the UK's blanket bogs, ecologists at the University of York have discovered.
Most of our drinking water comes from these upland peats and several iconic bird species such as the dunlin, golden plover and red grouse depend on these wetland habitats for nesting and feeding.
The scientists warn that climate change threatens these habitats, not only from rising temperatures increasing peat decomposition, but also via altered rainfall patterns ...
2015-07-31
Messenger (mRNA) molecules are a key component of protein biosynthesis. They are first transcribed as a "working copy" of the DNA and then translated into protein molecules. RNA-binding proteins such as RC3H1 (also known as ROQUIN) regulate the degradation of the mRNA molecules and thus prevent the production of specific proteins. Researchers at the Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC) have now shown that ROQUIN binds several thousand mRNA molecules. They demonstrated that ROQUIN also influences the gene regulator NF-kappaB, ...
2015-07-31
Parents' estimations of their children's happiness differ significantly from the child's own assessment of their feelings, a study has shown.
Research by psychologists at Plymouth University showed parents of 10 and 11-year-olds consistently overestimated their child's happiness, while those with 15 and 16-year-olds were inclined to underestimate.
Published in the Journal of Experimental Child Psychology, the study attributed the discrepancies to an "egocentric bias" through which parents rely too heavily on their own feelings in assessing the happiness of the family ...
2015-07-31
The humble butterfly could hold the key to unlocking new techniques to make solar energy cheaper and more efficient, pioneering new research has shown.
A team of experts from the University of Exeter has examined new techniques for generating photovoltaic (PV) energy - or ways in which to convert light into power.
They showed that by mimicking the v-shaped posture adopted by Cabbage White butterflies to heat up their flight muscles before take-off, the amount of power produced by solar panels can increase by almost 50 per cent.
Crucially, by replicating this 'wing-like' ...
2015-07-31
Main Finding(s): Women who participated in exercise as adolescents had a reduced risk of death from cancer and all causes in their middle and older ages.
Journal in Which the Study was Published: Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research
Author: Sarah J. Nechuta, MPH, PhD, assistant professor of medicine at Vanderbilt Epidemiology Center and Vanderbilt-Ingram Cancer Center in Nashville, Tennessee
Background: Understanding the long-term impact of modifiable lifestyle factors such as exercise in adolescence ...
2015-07-31
More time spent standing rather than sitting could improve your blood sugar, fats in the blood and cholesterol levels, according to a new study published today (Friday) in the European Heart Journal [1]. The study also shows that replacing time spent sitting with time walking could have additional benefits for your waistline and body mass index (BMI).
Researchers in Australia gave activity monitors to 782 men and women, aged 36-80 years, who were taking part in the Australian Diabetes, Obesity and Lifestyle Study. The monitors were capable of determining, very accurately, ...
2015-07-31
China needs to reduce its dependence on coal and improve the range of fuels it uses if it is to have long term energy security, according to new research from the University of East Anglia (UEA).
The study, published in the journal Technological Forecasting and Social Change, looks at the future of electricity supply in China and the issues it faces in reducing its carbon emissions - nationally China's electricity sector accounts for more than half its total greenhouse gas emissions.
The country's electricity sector is the largest in the world and energy security ...
2015-07-31
If it takes more than three trips to the GP to be referred for cancer tests, patients are more likely to be dissatisfied with their overall care, eroding confidence in the doctors and nurses who go on to treat and monitor them.
These worrying levels of dissatisfaction are based on further analysis of survey data from more than 70,000 cancer patients, by Cancer Research UK scientists at UCL (University College London) and the University of Cambridge, published today (Friday) in the European Journal of Cancer Care.*
Of the nearly 60,000 survey respondents diagnosed through ...
2015-07-31
On the 70th anniversary of the atomic bombs in Hiroshima and Nagasaki, a three-part Series published in The Lancet looks at the enduring radiological and psychological impact of nuclear disasters, including the most recent accident at the Fukushima Daiichi nuclear power plant in Japan in 2011. The Series provides vital information for the public health planning of future disasters to protect the millions of people who live in areas surrounding the 437 nuclear power plants that are in operation worldwide.
Although nuclear power plant accidents are uncommon, during the ...
LAST 30 PRESS RELEASES:
[Press-News.org] Shaping the hilly landscapes of a semi-conductor nanoworld
A new study reveals how hexagonal-patterned, self-organised hill structures emerge in 2-D at the nanoscale due to redeposition following semi-conductor bombardment with low-energy ions
