Week+of+3-4-2013

3-6-13 I came into the lab today and began scanning a sample of Octanethiol on Au(111) with Jolai. Here is a picture of the scope sitting in the ice-bath which allows for temperature controls and a larger temperature gradient between the cooled side and the heated side of Peltier. So far we've been able to run a 30 degree temperature gradient between the scope and structure housing the scope which will be incredibly useful for our experiments. Here is the scope with the glass covering to create a vacuum tight seal so that the nitrogen gas can be leaked into the system and all of the other gas is leaked out through the other gold hole in the back. BK- 8134.6 Å, 200 ms/line, 8 A/D. The main goal of the day was to get used to scanning with the new scope.Thankfully, I had a great deal of success with the scope today and the future with its experiments looks incredibly promising.

BL-8134.6 Å, 200 ms/line, 8 A/D BM-1000 Å, 32 A/D, 50 ms/line. The image below displays the first instance of atomic resolution I have been able to obtain with the new scope. The structured patterns that can be seen throughout this image are the Octanethiol molecules forming a monolayer on the surface. Using a function on the scope's software, Matt found that the length of one of the Octanethiol molecules was given at 30 nanometers. Previous experiments and information tell us that these molecules should be just under 5 nanometers and thus we have determined that there is a problem with the calibration of the scope. The size given by the software of this image is 1000 Å by 1000 Å but in reality, its length and width are actually about 1/6th of 1000 Å. This is a problem that can be easily fixed though and it should be by the next time I'm in the lab. BN-1000 Å, 32 A/D, 50 ms/line. BO-1000 Å, 32 A/D, 50 ms/line BP- 1000 Å, 32 A/D, 50 ms/line. Images BN through BP have a similar level of quality as they all clearly display the monolayer of Octanethiol on the surface of the gold. Furthermore, the tip was not eve that great as can be seen by the extra noise in each image which just proves more so that this new scope, because of its increased rigidity and resistance to vibrations, will be able to work more efficiently than the previous scope and we will be able to carry out more successful heating experiments.

BQ- 1000 Å, 32 A/D, 50 ms/line. There seems to be a large decrease in image quality here for reasons I do not exactly know. The underlying atomic structure of the surface is still somewhat visible but a great deal of the image is obscured by the noise caused possibly by the particular region I was scanning. The larger pits are a possible cause of this incredible drop-off in quality. BR- 1000 Å, 32 A/D, 50 ms/line. A similar level of clarity appears in this image, possibly due, again, to the pits present. BS- 2000 Å, 32 A/D, 50 ms/line. The image quality greatly increased with this image as the Octanethiol structures have once more become visible. One can see how they stack in patterns, especially across the upper third of this image. BT-2000 Å, 32 A/D, 50 ms/line. This is probably one of the best images of Octanethiol that I have ever scanned. The atomic structure is incredibly clear here and is typified by the stacking of its molecules into the ordered formation seen here. BU-2000 Å, 32 A/D, 50 ms/line. The image here still shows a high level of quality that is slightly lower than the previous one. It is incredibly interesting and encouraging to see how well this new scope has performed. The increase of pits present here is probably the cause of the decrease in image quality. BV-2000 Å, 32 A/D, 50 ms/line. I'm not quite sure as to why this image is so much blurrier than the majority of the rest of them but I think that it has something to do with the way it was processed. When I was editing it to include the relevant data points, I think I accidentally forgot to narrow the data plot to include only the points included in the actual scan. BW- 2000 Å, 32 A/D, 50 ms/line BX-500 Å, 64 A/D, 50 ms/line. BY-500 Å, 64 A/D, 50 ms/line. This image and the previous image, BX, show an even closer look at the surface of the gold and the Octanethiol molecules coated on top of it and these images were the ones we used to actually find out that the calibration of the scope was off because of how accurately and distinctly they are able to depict the surface molecules. BZ-500 Å, 64 A/D, 50 ms/line CA-500 Å, 64 A/D,25 ms/line CB-500 Å, 64 A/D, 25 ms/line CC-500 Å, 64 A/D, 6.14 ms/line. The obvious reason for the horrible quality of this scan is that the line time for this scan was so low that it was nearing the time taken by the feedback loop which means that it was getting to a point where it was barely scanning the surface at all. CD-500 Å, 64 A/D, 25 ms/line CE-500 Å, 64 A/D, 10 ms/line. Like CC, this image's quality is so poor because of the incredibly small scan line time. CF-500 Å, 64 A/D, 25 ms/line. This is a particularly peculiar image. I'm not exactly sure what exactly could have caused the wave-like structures in this image to appear. It could possibly be caused by a decrease in tip quality or by the nature of the surface scanned here which may have caused the tip to act strangely.

3-7-13 Today I came in to the lab and began scanning a sample of C-60. Matt and Ashley had been scanning on the scope when I came in and had just heated the sample for 3 seconds and were waiting for it to drift back in to scan the after images. The before regions that we were looking for are contained in AR and AS. I took over scanning beginning on AT.

AR-2.61 µm, 4 A/D, 300 ms/line AS-3000 Å, 64 A/D, 50 ms/ine AT-2.61 µm, 300 ms/line, 64 A/D. The long ridge in the middle of this image that runs across the whole thing resembles the similar structure in that of AR. I took a second image of the same region because the first one was in the Y-direction. AU- 2.61 µm, 300 ms/line, 64 A/D. Following this image, I moved the X-offset to the left to find the region scanned in AR. AV- 2.61 µm, 300 ms/line, 4 A/D. The region in this image almost identically resembles the one in AR. There don't seem to be any incredibly noticeable changes between the images. However, it is indeed promising to see that the sample can be scanned, heated, and successfully re-scanned with a limited amount of drift. AW-3000 Å, 50 ms/line, 64 A/D. I do not have any idea whether or not this region here resembles that in AS. In both, the image quality is fairly horrendous. They both look like a compilation of random streaks and neither of them contains any insight into the C-60 molecules on the surface, thus making this pair of images fairly useless in our analysis of surface changes but somewhat useful in our understanding of how the scope moves or drifts. Following this image, I heated the sample for 8 seconds. The tip crashed 7 seconds in and then uncrashed about 2 seconds after I stopped heating it. AX-2.61 µm, 300 ms/line, 4 A/D. Unfortunately, this region does not resemble the previous one in AV and I suspect that this is likely due to thermal expansion and cooling of the sample which prompted the sample holder to move just slightly. I zoomed in to the flat, light region in the middle. AY- 3000 Å, 300 ms/line, 64 A/D. I adjusted the drift after this image and fixed the Y-slope and took a second image of it. AZ- 3000 Å, 50 ms/line, 64 A/D. Following this image, I used the range function and heated up the sample for 7 seconds. The tip crashed right as I turned off the heater then immediately un-crashed. BA- 2.61 µm, 300 ms/line, 4 A/D. Once more, we have an image of what appears to be an entirely different region. I zoomed in to flat region on the left side of the upper third of the image. BB-3000 Å, 50 ms/line, 64 A/D. Like most of the images from today, there is not a very high amount of quality. This is probably due to tip quality or to the quality of the sample which is about equally as likely. After using the range function, I heated the sample up for 6 seconds and surprisingly, the tip crashed right when I stopped heating it and then un-crashed almost immediately following that.

BC- 2.61 µm, 300 ms/line, 4 A/D. Here we have another image of an entirely different area from the one that I am supposed to be looking for. It is also entirely possible that this could be the same region but the heat was enough that it changed the surface drastically beyond any recognition, though this is unlikely. I moved the region down because I thought the bottom third somewhat resembled part of BA.

BD-2.61 µm, 300 ms/line, 4 A/D. My idea, unfortunately, was incorrect. I zoomed in to the the flat region in the top half of the image. BE-3000 Å, 50 ms/line, 64 A/D. Following this image, I pressed range and then heated it for 5 seconds. Once more, the tip crashed right after I stopped heating it and then almost immediately uncrashed. BF-2.61 µm, 300 ms/line, 4 A/D. BG- 2.61 µm, 300 ms/line, 4 A/D. This image is of the same region as BF, just not the derivative plot of it. Nothing from this image appears to resemble any part of BC or BD which I think can also be attributed to drift caused by the thermal expansion and cooling of the sample. I zoomed in to the flat region in the upper left quadrant. BH-3000 Å, 50 ms/line, 64 A/D. I had to take this image several different times because of the drift that it kept experiencing so I could get the full image. Not much can be seen in this or in the following two images regarding the surface C-60 molecules, rendering them fairly unimportant for my research goals. BI-3000 Å, 50 ms/line, 64 A/D BJ-3000 Å, 50 ms/line, 64 A/D