Week+of+Sept.+8

Jun's Logbook

Started writing paper with an outline following the Siemens requirements shown below.

The purpose of this project is to design a setup in which a sample can be quickly heated with a laser during a scan with a scanning tunneling microscope. This project describes the design of the setup and interpretation of data. Designing a setup that allows the surface temperature of the sample to be altered very quickly can allow for a new range of experiments to be performed in scanning tunneling microscopy. Essentially, with a new method, new information can be gleaned from old setups simply by adding heat from a laser. There are few references that deal directly with the use of a laser as a heating method. However, lasers have been used for different methods. Erin Carmichael of the University of Illinois at Urbana-Champaign used a laser to excite electrons, but in this method heating was reduced as much as possible. No work on this setup has been previously done in the laboratory beyond the conceptual stage. Concept: The concept is to provide a way to //quickly// increase the surface temperature of the gold sample with a laser and (a) using the scanning tunneling microscope (STM) as a measurement tool of the temperature change and (b) record a change in the surface structure by taking images before and after using the laser. Calculations: This project was basically started from idea to realization. So the first step was buying a laser. In order to find an appropriate laser, initial calculations were done. Things incorporated into the calculations were dimensions of the gold sample, power of the laser, duration of exposure, and estimated temperature change. After the calculations, a 4-mW green laser was purchased. After the laser arrived, it was rigged so that it could be controlled outside of the STM box. Once the laser was setup inside the box, scans were done while turning the laser on for a period of time (10 – 15 secs.) then turning it off. Another setup was to take an image of the surface, turn the laser on for a longer period of time (10-30 minutes), then take an image after the exposure to see if any changes occurred on the surface. Setup/Materials: 4-mW green laser, sample holder with conical hole, vice-grip Data (Graphs/Images): The graphs of images showed an increase in height of about 5000 angstroms. This correlates to approximately a 15 deg. Celcius increase. The results show that a substantial temperature change can be obtained and controlled by using a laser. __Abstract__: In scanning tunneling microscopy most methods of heating samples are too drastic to allow for effective imaging due to the sensitive nature of the instrument. However, using a laser for heating does not add excess noise and can be easily controlled. From this concept, a design using a green laser can be implemented to heat the surface of a sample. Considering the size and thickness of the gold on mica sample, a 4-mW green laser suffices as a source of energy. The scanning tunneling microscope (STM) is used to measure the temperature change as the laser is exposed to the back of the sample. After about 25 seconds of exposure, the heat gain equals the heat loss. Using the STM, the expansion of the sample is measured at about 5000Ǻ which correlates to an approximately 15°C difference. This finding shows that a heating method within the environment of the STM can be controlled and effective.
 * Purpose of the research:** Describe the problem to be solved, the research question to be answered, the hypotheses to be tested, or the product to be developed.
 * Rationale for the research:** Why is the work important?
 * Pertinent scientific literature:** Provide a brief review of the most relevant literature. Previous relevant publications and patents must be cited in the text of the Research Report.
 * Prior work and contributions of others on this project:** Provide information on concurrent similar or related work, projects, or both in the facility or laboratory in which you worked.
 * Methodology:** Describe the methods used to allow someone trained in the field to understand the work or sufficient steps to follow a proof. Explain what was done and how it was accomplished. Document any outside assistance or special circumstances that had implications for the project.
 * Results:** Describe the results of the research or mathematical study.
 * Discussion:** Describe how the results address the problem to be solved or research question to be addressed. Discuss any interpretations that can be drawn from the results.
 * Conclusions:** What questions still need to be answered? Does the Research Report have a basis for future work?
 * References:** Assemble a complete list of the works cited in the paper, formatted correctly for the discipline.