Miniaturized electronics have a bright future thanks to new techniques proposed by Khalifa University researchers that speed up the discovery of unique “ferrovalley” materials.
Valleytronics—from ‘valley’ and ‘electronics’—is an exciting research field in the semiconductor industry that researchers are eyeing as a faster way to store and process data.
Semiconductor technology is currently based on the manipulation of the charge of electrons. When excited, electrons jump the material bandgap and become charged, and this charge is used to store and process information. In addition, electrons also have additional degrees of freedom, such as spin and valley, that can encode and process information.
Dr. Abhishek Sharan, Postdoctoral Fellow, and Dr. Nirpendra Singh, Assistant Professor, developed new ultra-thin magnetic semiconducting materials, known as ‘ferrovalley’ materials, using a prediction algorithm and revealed these 2D materials that can be used to develop the next generation of miniaturized electronic devices. Their results were published in Advanced Theory and Simulations. Their work has been featured on cover page of the journal’s April 2022 edition.
“In the past decade, valleytronics has opened up a wide platform of research for discovering new materials exhibiting valley polarization for storage and information processing,” Dr. Singh said. “2D materials are an exciting category of materials in this class, with 2D ferrovalley materials particularly interesting and highly sought after as they exhibit intrinsic magnetism.”
“In ‘ferrovalley’ materials, in addition to charge and spin, the electrons possess another degree of freedom known as the valley degree of freedom,” Dr. Sharan said. “These materials exhibit two unequal energy levels along two equivalent valleys that the electrons can occupy. The electrons can be manipulated so as to occupy a specific valley in a controllable manner, which can be used to encode and process information in ways that go beyond conventional charge-based electronics.”
In traditional computing, computers represent information in binary code, which is written as sequences of 0s and 1s. Information exists in one of two states: 0 (no charge) and 1 (charged), which translates into “on” or “off.”
With valleytronics, the same applies but with additional enhancement: one valley or the opposite valley in addition to on or off, 1 or 0. Therefore, the electrons now have four degrees of freedom.
“If spin is involved too, as in spintronics, electrons possess eight possible states,” Dr. Sharan added. “With more degrees of freedom, more information can be stored, paving the way to speedy, energy-efficient, and miniaturized devices.”
Manipulating this additional degree of freedom – switching an electron from one valley to the other – requires an energy input and a lot of energy at that. The valley polarization can be achieved using light waves, where the electrons jump between the valleys. But this process is dynamic and has a limited lifetime.
The other way to do it is magnetic proximity. But adding an external magnetic field increases the device’s energy consumption and means the device needs to be larger, negating its use in miniature electronics.
Ferromagnetism is the fundamental mechanism by which certain materials, such as iron, cobalt, and nickel, form permanent magnets or are attracted to magnets. Only a few ultrathin substances display ferromagnetism, and experimental discovery of these materials is a daunting process. However, a computational model would speed discovery significantly.
The KU research team used a novel prediction algorithm to identify two monolayers that exhibit intrinsic magnetism and spontaneous valley polarization, adding two new materials to the list of ferrovalley materials for experimental realization. The two materials they identified are Lanthanum iodide, LaI2, and Praseodymium iodide PrI2. Both LaI2 and PrI2 are similar in structure to Molybdenum disulfide, MoS2, which is a well-known and effective 2D semiconductor material already in use in microelectronics but does not exhibit intrinsic magnetism.
“Both LaI2 and PrI2 are exciting candidates for valleytronics applications,” Dr. Sharan said. “We’re expecting great experimental results from these two newly identified ferrovalley materials.”
22 March 2022