INTRODUCTION

1. Evaporated Gold Slide Bucky Paper Sample Evaporated Gold Slide Evaporated Gold Slide SM-015-02 (Green) SM2 Evaporated Gold Slide SM-019-05 (Orange) 8 1 8 1 8 8 1 1 8 1 7 2 7 7 7 2 7 2 2 2 Graphite Sample 6 3 6 3 5 4 5 4 3 3 3 6 6 6 Sliver Paint Contacts 5 4 5 4 5 4 FIGURE 3. Samples SM-019-05 & SM-015-02 SM-019-05 Current was 5,8 and Voltage was 6,7 SM-015-02 Current was 1,4 and Voltage was 2,3 FIGURE 4. (TMBMT-TTF)2Iat 10 µA of current Current was 5,6 and Voltage was 4,7 FIGURE 5. Graphite at 10 mA of current Current was 4,7 and Voltage was 5,6 FIGURE 6. Bucky Paper measurement at 1 mA of current Current was 5,8 and Voltage was 6,7 Physical Characterization of Novel Organic Materials Rebecca Shea Kelly Department of Chemistry, University of Alabama at Huntsville, Huntsville, AL 35899 National High Magnetic Field Laboratory, Tallahassee, FL 32310 INTRODUCTION Novel organic materials are important materials for technology because they are easy to make and cost efficient. The purpose of this investigation was to examine the physical characteristics of these materials. The factors that were measured were temperature dependence and resistivity. Two representative standards were measured as well as three synthesized compounds. METHODOLOGY Tetrakis(methylbenzoate-4-methylthio)tetrathiafulvalene iodine or (TMBMT-TTF)2I, SM-019-05, and SM-015-02 Crystals were obtained from Dr. Brian Ward and Sharzod Madrahimov at the University of Alabama at Huntsville [1]. The crystal structure for (TMBMT-TTF)2I can be seen in FIG 1. The crystal structures for SM-019-05 and SM-015-02 have not yet been identified. The crystals were microscopic in size or powders. This made the fine gold wires impossible to paste to the samples. Therefore a new method was made to measure the samples. This method was termed Spiderman. Please see FIG 2 for the design of Spiderman. The samples were placed on an evaporated gold slide that was etched to create the terminals. The gold slide was placed on a Pelletier junction, which was used for the temperature control of the samples. For (TMBMT-TTF)2I, SM-019-05, and SM-015-02 a four terminal setup was used for the sample measurements. Please see FIGS 3-6 for a representation of the samples on the evaporated gold slides along with their terminals used for measurements. FIGURE 10. Resistivity vs. Temperature with V-I Curves at Room Temperature and at Helium Temperature for Bucky Paper FIGURE 11. Natural Log of Resistivity vs. 1/T for Bucky Paper Sulfur Iodine RESULTS FIGS 7-9 show that the samples measured are semi-conductors. This means that as the temperature increased, the resistance also increased. The samples were ranked least conducting to most conducting. FIG 10 shows the resistivity versus temperature for warming up and cooling down for the Bucky Paper sample. The currents used were 0.1 mA for warming up and 10 mA for cooling down. The V-I curves are shown for room temperature and helium temperature with room temperature being linear and helium temperature being non-ohmic. Bucky Paper was found to be a semi-conductor. FIG 11 shows the natural log of resistivty versus the inverse of temperature at the same currents for warming up and cooling down. It does not follow the usual pattern of activation energy (Ea) so it could not be determined for this sample. FIG 12 shows the resistance versus temperature for graphite. Graphite is metallic because as the temperature decreases, resistance decreases. FIG 13 shows the I-V curve for graphite and (TMBMT-TTF)2I. Graphite is linear, and (TMBMT-TTF)2I is non-linear. At room temperature, (TMBMT-TTF)2I has the resistance of 1.24 mega Ohms and at 42°C, it has the resistance of 1.01 mega Ohms. Based on the results from this investigation, (TMBMT-TTF)2I would be a better conducting material than the SM-015-02 and SM-019-05. Given that the Spiderman method gave decent results in this investigation, large crystals are not necessarily needed for physical characterization tests. Benzene ring Ester group FIGURE 1: Crystal Structure of (TMBMT-TTF)2I FIGURE 13. I-V Curve for Graphite and (TMBMT-TTF)2I FIGURE 12. Resistance vs. Temperature for Graphite CONCLUSIONS In conclusion, I wanted to investigate the physical properties of various novel organic materials. Since the samples were microscopic or powders, the method I used for measurements in this investigation was Spiderman. Bucky Paper and Graphite were used as representative standards to show what to expect for the samples. Bucky Paper was determined to be a semi-conductor with the amount of current being an important parameter for measurements. With semi-conductors, the value of the current was found to impact the results. This is due to the heating and/or non-linear effects. With metals, Ohm’s law (V=IR) should be obeyed. The sample of graphite was found to be metallic because as the temperature decreased, the resistance did also. Ohm’s law was obeyed because as the current increased, voltage also increased to give a linear graph.  (TMBMT-TTF)2I, SM-019-05, and SM-015-02 were found to be semi-conductors which means that as the temperature increases, resistance increases. (TMBMT-TTF)2I was the better conductor out of all three samples. It is a charge-transfer salt between the TTF functionalized donor cations and iodide anions.  In this salt the iodine, I2, which was used in the reaction, oxidizes the TTF functionalized donor molecules. Since Iodine is a good oxidizing agent, it is reduced from I2 to 2I-. SM-015-02 was the most insulating due to its high energy gap of 795 K. Based on this investigation, if a synthetic chemist wanted to make a conductor, (TMBMT-TTF)2I would be a better conducting material than the SM-015-02 and SM-019-05. FIGURE 2. Pictures of Spiderman Sample Least Conducting Most Conducting REFERENCES 1. Graduate Student-S. Madrahimov, B. Ward, Private Communication ACKNOWLEDGEMENTS I would like to thank Dr. James Brooks, Dr. David Graf, and Ade Kismarahardja for their help and patience this summer. Dr. Brian Ward, and Sharzod Madrahimov for the crystal samples. This work was supported by the NSF, NHMFL, and FSU. FIGURE 8. SM-019-05 (Orange) FIGURE 9. Tetrakis(methylbenzoate-4-methylthio)tetrathiafulvalene iodine FIGURE 7. SM-015-02 (Green)