This is the best description I have of my senior project this far. The following document is actually a grant proposal I wrote to get the $468.55 that I needed for certain supplies.

Purpose

The purpose of this project is to determine the morphological structure of tetrakis(4-carboxyphenyl)porhine (TCPP) films. (Terui et al., Structural study of porphyrin isomers on metal substrates by using STM)

To begin, a determination of how these molecules lie on the substrate will be conducted.

Metalloporphyrins such as TCPP are useful for their biological functions (D. Dolphin, The Porphyrins), use as chemical sensors (Paolesse et al., Porphyrin thin films coated quartz crystal microbalances prepared by electropolymerization technique, and potential use in spintronics (Scheybal et al., Induced Magnetic Ordering In a Molecular Monolayer) (devices that utilize the magnetic orientation as an information carrier).

With a better understanding of TCPP films it will be possible to improve the theoretical calculations of the qualities of interest, electronic structure & properties. This in turn assists experimentalists to actually find and utilize the qualities of interest.

Hypothesis: The TCPP samples lie parallel to the plane of the substrate, and provide a good basis for further work in determining a crystal formulation of TCPP.

Description

Sample: Inserting manganese (Mn) in the center of TCPP, and Nickel (Ni) at the bridge sites between the macromolecules as shown in the above image gives TCPP magnetic qualities, and potentially allows it to move charge carriers with a specific magnetic alignment through an electronic block.

Measurement: In conjunction with an atomic force microprobe (AFM), scanning tunneling microprobe (STM) measurements can help determine the structure of the films as they stack.

Prior research has attached molecules of tertiary-butyl-methoxy-phenyl-porphyrin (TBMPP) to a gold (Au) substrate(Terui et al., Structural study of porphyrin isomers on metal substrates by using STM). The resulting STM image presented by Terui et al. is shown below in part a.

The image shown above (part b) shows that the copper (Cu) substrate doesn't present an orderly arrangement like the Au substrate.

Although the molecules (TCPP, TBMPP, TBPVPP) differ in their attached phenyl groups, the structures are similar enough to give an idea as to how porphyrins attach to these two substrates. This suggests a gold substrate is more appropriate for the work at hand.

By following procedures established by Scuderio et al., Scuderio et al., and Terui et al., preliminary images may be gathered. These preliminary images may be analyzed for improvement as well as whether a determination can be made from the images.

This is the abstract for research I performed in the summer of 2006 at Oak Ridge National Laboratories:

Dilute-magnetic semiconductors (DMS) are promising materials for spintronic applications (electronics that take advantage of spin to carry information). Ga_1-xMn_xAs is the most commonly studied DMS system. The direction of the ferromagnetic ordering in a quantum well model of Ga_1-xMn_xAs with doping x is determined. The magnetic order is perpendicular to the plane for low carrier densities, n < n₁, and becomes parallel within the plane for higher carrier densities, n > n₂. However, it is not known if phase separation occurs between regions having carrier density n₁ and moments pointing perpendicular to the plane, and others having n₂ > n₁ and moments within the plane. Phase separation occurs in the system if the chemical potential at two different fillings is the same. In this project, the first two wave functions of the carriers in the quantum well were used to calculate the energy of the system as a function of angle and carrier density. The energy was minimized with respect to angle, and the chemical potential was calculated. A Maxwell construction indicated phase separation occurs between n₁ = 3.1% and n₂ = 5.3% for x = 0.35. The complete phase diagram for this system was calculated, and distinguished between the phase separated, parallel phase, and perpendicular phase regions for different amounts of dopant. Phase separation of the ferromagnetic phases in a quantum well may imply that some regions may be magnetically ordered up to higher temperatures. This might allow the design of spintronic devices that can operate at room temperature.