Week+of+9-21+and+9-22

9-21-11 I was unable to go into lab today so I decided to look up some information on the Scanning Tunneling Microscope. I found a video that shows how the STM works on youtube at the atomic level. media type="youtube" key="5g43LWUl18Y" height="360" width="480" Also, after doing some research, I found out that lots of noise is bad during scanning because of the vibrations of the soundwaves. These soundwaves vibrate the surface of the gold and make it harder to get a clearer image. ( [] ) I also looked up how a STM functions. The STM moves the sample close towards the sample in a coarse manner until the sample is in a close enough position. Then, the movements are controlled mainly by piezoelectric fluctuations. The STM will not approach close enough to the point where it will have made contact with the sample. The STM will leave a very small separation between the tip and the sample. The STM then applies a current and begins to tunnel. Once tunneling has begun, the tip's current and position in correspondence to the sample and the data are obtained from the resulting changes in the current.The tip moves across the surface in the x-y plane. The changes in surface height and density result in changes of current. These changes in current are the resulting images which we see. 9-22-11 I came in at around 3:20 today and Natalie brought me the sampleof Octanethiol on Au(111) that Annette had prepared for me. I screwed the cover of the piezoelectric power supply back on to the box. After this I began scanning the Octanethiol on Au(111). I spent about an hour and a half changing tips and trying to scan without getting any good areas. It was 4:30 p.m. when I found my first pretty good area to scan. However, while scanning, about halfway through the image, the sample holder moved slightly backwards and I was unable to finish the scan. At 4:47 p.m. I got my first scan of the day. At 5:17 I had taken a total of five pictures. As the day went on, my images improved in definition and in the amount of features in them. Image "AF" was the first image I found that was worth shooting with the laser. I brought the piezoelectric power from 40.0 V to 5.0 V then shot the laser for 50 seconds. I let the sample cool for 2 minutes then brought the power back up to 40.0 V. It's not very clear if the after image is the same area as the before image. However, when i was scanning the after image, the image bottomed out halfway through the first two times I tried to scan it. The third time it did not do this until the end of the image.The images today were not particularly spectacular but they also were not horrible. The last few images showed some definition and features and as the day went on they did improve. This is most likely due to the quality of the tips rather than that of the sample.

9-22-11AA media type="custom" key="10572658" This was the first image of the day and it showed no real definition or distinct features. There is no real evidence of the Octanethiol on the surface in this image. This image has a lot of noise also. 9-22-11AB media type="custom" key="10572670" This image shows a high amount of noise slightly above the middle and in the bottom part. There are slightly recognizable features on the right side but it's hard to tell what exactly these features are.

9-22-11AC media type="custom" key="10572680" This image most likely shows a double tip copying the same image on the top that seems to have been started. There's a lot of noise on the top where there are some recognizable features.

9-22-11AD media type="custom" key="10572692" This image has a few valleys on the right side and a few valleys and hills on the left side. There's a lot of noise in the image. 9-22-11AF media type="custom" key="10572698" This image shows a lot of distinct features but I believe that a double tip was used here because a lot of the features show up right next to each other but in a faded manner such as the hill in the top right corner and the many valleys throughout the image. I did laser this image because of all of the distinct features on it for fifty seconds. 9-22-11AG media type="custom" key="10572704" This image is the after image of 9-22-11AF. I let the sample cool for 2 minutes before scanning. There are a lot of valleys throughout the image and a few hills. The image shows a lot of noise and right before the end of the image, the sample holder seemed to have moved backwards on its own resulting in the bottoming out of the image. 9-23-11 I went to Quarknet on this day and we learned about different MATLAB functions and variables. I was given the first chapter because I could not go the week before along with a packet of exercises.