Week+of+4-18+and+4-19

4-18-12 I came in today and began scanning a sample of Octanethiol on Au(111) that Natalie prepared. After a short time, Professor Kandel came in and talked to Guido and me about a new project.He wants me to continue in the direction of thermal expansion but he wants us to start using electrical currents to heat the sample rather than laser heat because of the low success we have had with it. The idea is to send a current through a wire connected to the sample. Here is a sample of Gold on micah. As the current passes through the gold sample, the electrons that will pass through to the other wire will cause friction and create heat. However this will only work if the gold is a strong enough resistor. Guido and I began testing the resistance on old samples of Gold. They would usually have a resistance of about 0.6-0.9 Ohms. Professor Kandel suggested that we should use a razor blade and cut different sections on the surface to increase resistance. We tried out several patterns: straight lines up and down, straight lines across, diagonal patterns, and various others. One of the patterns we tried is below. The highest resistance we were able to achieve with one of these patterns was 3.2 Ohms. We might be able to get a higher amount if we are more careful with the cutting.

We told Prof. Kandel at around 5:30 that we were able to get up 3.2 Ohms of resistance and he advised us to begin the next stage of trying to see if the project will be able to work which is finding a way to connect the wires stably. He told us to talk to Matt but Matt had already left so we will speak with him either tomorrow or next week. Afterwards, I resumed scanning. The first scan had lots of noise. I cut the tip halfway through.I was unable to scan any decent images for the rest of the day. 4-19-12 I came in today and began scanning the same sample from yesterday. The first attempt crashed into the tip. I pushed it back slightly and approached again. It worked this time. The image quality was absolutely horrible though. I cut the tip. The next scan worked without crashing. I zoomed in to the middle region of "AA". "AA" was somewhat decent but also had a fair amount of noise. I shot the laser at "AB" for 40 seconds. I withdrew it a small bit before shooting. I let the sample cool for 2 minutes afterwards. I attempted to scan and got a horrid image. I tried readjusting but got a similar result. I decided to just cut the tip and try with a new region. I then took "AC" which was also a fairly good image. I withdrew the sample, shot the laser for 55 seconds, and then let it cool for two minutes. I tried approaching and it was very fidgety. I withdrew it and tried again multiple times without success. I cut the tip and scanned again. "AD" had some pretty good features. I zoomed in to the left center of it. "AE" was also had decent features but was a bit blurrier than "AD". I changed the tip after it. The next two scans were horrible and I did not finish either of them. 4-19-12AA This image has a fair amount of features. They are not overly dense. Most of them are pretty easy to see but others require a closer look. The junk in the top right corner is indicative of a poor tip as the streaks of the image are most visible here. I zoomed in to the central region to the right of the largest crater. 4-19-12AB The features in this image do not have very well-defined boundaries. The poor quality of the tip is much more clear in this image. In the last one, closer parameters were not used so it was not as easy to say if it were a bad tip. With the results here, we can say fairly certainly that the tip is poor and needs to be changed. 4-19-12AC The boundaries of the features in this image are not well-defined. There is not a clear line that separates the clumps of Octanethiol from the rest of the surface. The general haze and the ridges on the right side give the most clue that the tip is of low quality. 4-19-12AD The top left corner of this image is a very blurry region. The lower half of this image is mostly unintelligible because of the large discrepancy in elevation between the middle and the sides. The features that one can see are fairly interesting but do not look too defined. I zoomed in to the region on the left side. 4-19-12AE This image is very fuzzy. It even appears to have a double tip at points because of the incredible blurriness. The rift on the left side shows pretty clearly that the tip is not very sharp but is most likely very dull. The features are not very insightful unless the structures on the hill in the bottom left turn out to be Octanethiol molecules. However, it is unlikely.