Week+of+1-18+and+1-19

1-18-2012 I came in today and began scanning a sample of Octanethiol on Au(111) that Becky prepared. The first two scans both bottomed out halfway through for some unknown reason. After two more attempts of failed scanning and approaching, I changed the tip and cleaned the sample holder and the STM. The failed attempts continued. There have been no good scans so far and it's already five o'clock. It is noisier in here than usual today. After several more failed attempts the STM stopped working and no longer connected to the computer. I disconnected all of the wires from the STM to its transfer box and the wires from this box to the computer. I reconnected them and it worked. However, each time I attempted to approach, the tip would crash. I was unable to get any scans of gold surfaces until 5:50 p.m. Even this scan was horribly poor and not even worthy of finishing. I think these poor results were caused by both the increased amount of noise in the lab today and the poor quality of tips used while scanning. These poor results could have been also caused by a poorly made sample. I hope I will be able to gain better results tomorrow and plan on trying to cut the tips much more sharply. 1-19-12 I came in today and began scanning a sample of Octanethiol on Au(111). It is the same sample from yesterday. My first scan kept bottoming out halfway through so I moved the sample and changed the tip. The next scan simply had bad quality so I cut the tip and moved the sample again. The same went for the next few attempts. I finally got a decent image at around 4:45 p.m. after numerous tries and several switched tips. I zoomed in to the bottom right quadrant of this image, "AA". The zoomed in image, "AB", was fairly blurry but I decided to shoot the laser at it to test the possibility that there was enough rom for thermal expansion while scanning with the Piezoelectric stack charged with 50.0 V. Also, there were a large amount of features and I wanted to see what happened. I brought the voltage from 50.0 V to 5.0 V. I shot the laser for 45 seconds then let the sample cool for four minutes. I noticed, however, that the sample crashed when I had brought the voltage of the piezostack down. I decided to continue with the lasing and try to fix it afterwards. After applying the laser, I retracted the sample holder a few times then brought the voltage back up to 50.0 V. I then approached and got a somewhat similar area. I changed the tip after this after image because of its incredibly high amount of noise and blurriness. Several more failed scans prompted several tip changes and cuts. I was unable to procure another decent image for the rest of the day. There are several different possible reasons why I was unable to obtain any useful results today: noise in the lab caused by Matt's vacuum pump, possibly dull tips, and possibly a damaged or dirtied sample, seeing as how it was not placed in a foil-covered vile when I came in yesterday. Hopefully with a new a sample next week, results will improve. 1-19-12AA media type="custom" key="12153540" This image shows an incredibly high amount of features, one of the highest I have ever seen. The features are very evenly spread out throughout the image and there is not one single place that holds a majority of the features. The main problem with this image is the lack of definition caused by a poor tip. Because of my lack of results today and yesterday, I wanted to to test the laser function, specifically the difference in voltage necessary for thermal expansion. That is why I zoomed in to the bottom right quadrant. 1-19-12AB media type="custom" key="12153544" This image showed the lack of definition as indicated by the last image. The noise is amplified in this image and it is clear that we will not be able to learn anything about Octanethiol molecules on its surface from this or from the after image. 1-19-12AC media type="custom" key="12153576" This image shows a slight bit more noise than the first one and the features seem much less defined in this image. There may some credibility in the hypothesis that the laser causes thermal expansion in the tip and ultimately results in a flatter, duller tip. AB-AC media type="custom" key="12153660"