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Because Google uses Blogger and I use Google I decided to move this blog from WordPress over to Blogger. http://magnusblogofphysics.blogspot.com

My thesis is finished

My thesis “in-situ TEM probing of nanomaterials” is now finished. In Sweden, a thesis is a comprehensive summary of the included scientific work. The paper versions of the thesis consists of two parts the summary, part one, with the scientific papers, part two, attached into one volume. Here is a link to the comprehensive summary part of the thesis.

In-situ electromechanical resonance of nanowire

New movies on annealing of nanowires

I have put up the annealing nanowire movies at YouTube.

Movie of real time electron diffraction on nanowire annealing.
Movie showing a nanowire straightening out due to electric heating.

Plot of resistance as function of melted particles

This is a plot of the sintering process, resistance as function of melted particles.
The resistance is shown to go up during the process. It’s hard to say anything more about the behavior of the system. But at least due to the resistance increase, some of the current appears to go through the particles, not to surprising perhaps. The final resistance is on the other hand quite low meaning that good conduction still exist after the particles melted away.

Sintering Summary

This is a table summary of the power and voltage settings required for the sintering process. Regarding the physical dimensions of the sample, no correlation to sintering power, or required potential is being found.

File	Lenght(nm)	Area(nm2)	Power(uW)	Potential(V)
0116-04	393	80000	100	1.7
0116-05	252	48800	7	0.19
0119-02	585	201500	5	1.5
0119-05	224	76500	20	2.0
0119-13	487	49900	1	1.95
0122-01	411	15100	4	8.04
0122-02	465	38100	0.5	7.0

The area is the occupied space of the sample in the viewing plane. (Gives some estimate on sample size). The length is the probe to probe distance, measured with a mean error of 55nm.

Pre-phase sintering plots…

Improvment on meassured variables

By meassure the best known variables, noise-ratio was imroved.

By measuring the best known variables, applied bias voltage U, electric current I and the known series resistor with resistance Rs. The unknown variables of the sample, potential drop Up, sample resistance Rs, power in sample Pp was calculated with lesser noise.

I have remade the plots with this new approach and it clearly shows much better noise-ratio than before. The calulations before were made by using the noisy-value of the measured potential drop over sample.

By meassure the best known variables, noise-ratio was imroved as shown in this plot.

The sintering image folder at flicker shows you the other plots that were remade.

Details on the sintering process of the nano particles

When the particles fuses together conductance increases. (exp. 0119-02)

I have now made some detailed plots on the observed current-jump that occurs when the nano particles fuses together. This was observed for seven of the eight experiments.

In the box archive I have put a data table for the results on the electrical properties. The samples don’t have so well defined geometry, but at least they can be aranged unde some basic shapes as wire-, cluster- and grape-shaped. In three cases the need power to sinter the particles was below 1~uW, two cases at 5.9uW and 7.1uW and another two cases at 23.5uW and 34.2uW which is the highest value of them all.

Detail study on the melting of one nanoparticle

TEM images before- and after-melting of one particle.

Detail plot when one particle melts.

In this experiment we manged to study the melting of one single silver nano particle of size 50 nm. What we do is driving a electric current through the sample and continually increasing the power which results in melting of the particles. After the particle have melted a carbon-shell is left behind and the resulting drop in electric resistance is about 800 Ohm.

If one checks the movie from the experiment, one can see that in the beginning of the experiment the same contact particle as mentioned above melts a little with a resulting small decrease in size followed by a resistance increase of 240 Ohm.