Acknowledgments

1. Examining an n-doped Ge Crystal Under the B-Field and Temperature Variations Adam W. Keller & Shouvik K. Bhattacharya Fall 2013 | Department of Physics | Creighton University | Omaha | NE 68178 AbstractAn n-doped Germanium crystal on a circuit board was studied under a changing magnetic field with a constant temperature. Data were obtained using the LabView program. Charge densities and conductivity of the sample were determined from the results. When a magnetic field is applied perpendicular to the current flow, a voltage difference occurs near the edge of the n-doped Germanium crystal. This voltage is known as the Hall Voltage. A Hall-voltage is used to study properties of semiconductors. In this experiment, an effect of the Hall Voltage on an n-doped Ge crystal was studied at a constant temperature and changing magnetic field. Introduction Results Conclusions The resultant Hall voltage in a sample is dependent upon both the environment the sample is in and the physical properties of the sample itself. With analysis of the environment, the hall voltage produced can be used as a means to probe the physical properties accurately. Figure 2. A Circuit Diagram of an Op-amp and a transistor Figure 4. Hall Voltage as a Function of Current Further Study We did not get a chance to acquire data in higher temperatures. For future studies, it is recommended to observe what happens to the Germanium crystal with the presence of a magnetic field in higher temperatures ; most notably, how the conductivity varies. Methods In order to study the Ge-crystal we designed a wooden bench to put the sample within the electromagnet’s center. We mapped the magnetic field inside and outside the electromagnets ( Figure 1). To control current using the LabView program, we attached an Operational Amplifier and a transistor in a negative feedback loop (figure 2). Other methods of current control are available, but this method was the simplest to calculate. Figure 5. Further analysis of figure 4 Figure 3. The VI is ready to collect Data References Electronics quiz of the day. (2010, November 18). Retrieved September 2013, from EEWeb: http://www.eeweb.com/electronics-quiz/solve-the-current-through-the-load-of-this-handy-current-source Sidebottom, D. L. (2012). Fundamentals of Condensed Matter and Crystalline Physics. Cambridge University Press. The VI can control all aspects of the experiment (current, temperature, and all measurements) except for those pertaining to the magnetic field. This allowed great stability in values. Utilizing figure 5, This shows that the carriers are negatively charged. Additionally, • Acknowledgments • We want to thank the Department of Physics at Creighton University, Drs. Michael Nichols, Andrew Baruth, and Mr. Brad D. Walters for help in carrying out this experiment. Figure 1. Magnetic Field inside the core versus Magnetic Field outside the core