Traditionally, data processing relies on the “charge” of an electron, however a new technology called “Spintronic” is looking to turn the semi-coductor industry on its head by using an electron’s “spin” instead. This development should allow for high speed, micro-sized, and highly efficient storage and data processing semi-conductors.
The most important development for spintronics has been the development of dilute-magnetic semiconductors. These semiconductors are similar to traditional semi-conductors, however magnetic atoms are added, making the semi-conductors ferromagnetic. Ferromagnets are permanent magnets. This represents a significant step forward as one of the largest impediments to understanding ferromagnetism in dilute-magnetic semi-conductors has been removed.
This research is the result of the coordinated efforts of numberous researchers under the leadership by the U.S.-Department of Energy’s Berkeley Lab. By using the new Hard x-ray Angle-Resolved-PhotoEmission Spectroscopy (HARPES) technique scientists have discovered that gallium manganese Arsenide gains its ferromagnetism from two separate mechanisms.
The speed and power of semiconductors are greatly determined by the materials they are constructed from. In is the micro-sized pathways, switches, and circuitry inside of the semi-conductor that gives it its properties. Until now, it was very difficult to probe into the deepest and smallest layers of semi-conductor technology. When scientists probe deep into materials with traditional methods they interfere with the delicate systems, distorting its properties and consequentially the research. HARPES allows scientists to dig deeply without interfering with the inner workings.
By using high photon energy x-rays, or so-called “hard” x-rays, scientists have been able to knock off photoelectrons from their orbits deep within the semi-conductor. This allows analyzers to pick up a stronger “signal” from within the semi-conductor and to be able to properly map out the semi-conductors inner workings.
Gallium Magnesium Arsenide (GaMnAs) is widely used in semi-conductor technology, trailing behind only silicon in usage. Using HARPES, researchers were able to probe the electronic-bulk structure of the GaMnAs.. Researchers found that by replacing a small number of gallium atoms with manganese atoms they could create a dilute magnetic semi-conductor. Such a conductor is well-suited for the spintronic devices mentioned about and could lead to major breakthroughs in material science.
Previously, researchers have only been able to make dilute magnetic semi-conductors out of Gallium Arsenide when operating at high temperatures that are simply not feasible for computing applications. Scientists now believe that with recent breakthroughs they will be able to make a semi-conductor from Gallium Magnesium Arsenide that operates at room temperature.
Using HARPES scientists have begun to decode the complex magnetic processes within the semi-conductor. With HARPES scientists have been able to figure out the “bands” at which Gallium-Manganese Arsenide start to exhibit dilute magnetic properties. This fundamental breakthrough in understanding should help lead to major advances in semi-conductor technology and will lay the foundation for creating dilute magnetic semi-conductors that can be operated at room temperature and can be used in computing process.
Before HARPES there were two primary explanations for the-source of ferromagnetism in dilute-magnetic semiconductors, the “p-d exchange model” and the “double exchange model.” These two models offered differing explanations of how ferromagnetism occurs among electrons in differing valence bands. Interestingly, HARPES proved that both models are correct and co-exist within the semi-conductor.
This is the first time that HARPS has been successfully applied to uncover a problem as the forefront of materials science. This important breakthrough represents just the first step in the use of HARPES, which stems from the photoelectric effect first outlined by Albert Einstein in 1905. HARPES allows scientists to problem deeper into materials with minimal interference or contamination. This allows scientists and researchers to gain a better understanding of the inner-workings of various materials.
The research was headed by the eminent Professor Fadley, appointed at both UC-Berkeley and UC-Davis. The research is described in an article entitled “Bulk-electronic structure of the dilute-magnetic semiconductor GaMnAs through hard X-ray angle-resolved-photoemission.” The article can be found in the journal-Nature Materials. The research was supported by the Department of Energy’s Office of Science. Major portions of the study itself were conducted at the Spring8 synchroton radiation facility which is located in Hyogo Japan under the care of the Japanese National Institute for Materials Studies.
More research using the HARPES technique is now being planned by universities around the world, with breakthroughs promising to revolutionize the semi-conductor field.