A1.

Project title: Computer memories of the future.

 

Any computer or portable device makes use of mainly three different technologies to store and retrieve information: the magnetic hard disk (HD), the dynamic random access memory (DRAM) and the FLASH memory technologies. The combined use of three different technologies is due to the need to overcome the limitations shown by each of them. The magnetic HD provides the largest possible data density but it makes use of sophisticated mechanics. This brings three consequences: a magnetic HD is slow, energy consuming and delicate, the last two limitations being hardly acceptable in portable devices. Semiconducting FLASH memories, widely used in pen drives and memory cards, are non-volatile, too. This is why they are considered to be the best candidates to replace the magnetic HD drives. As a matter of fact, solid state HDs based on FLASH technology are already available on the market. After only a few years from their commercialization, this solid state HDs already seem to have reached a limit, despite the fact that the memory capacity remains one order of magnitude smaller than that of a standard magnetic HD. The limit is, in principle, the same as that limiting the performance of the very fast DRAMs: the information is retained by storing charge and the charge always leaks, either through the tunnel barrier, when it is made as thin as possible to increase velocity, like in DRAMs, or through the barrier sidewalls, when the bit cell is made as small as possible to increase density, like in current solid state HDs. This consideration seems to suggest that the memories of the future might still make use of magnetic materials. By using such materials, one does not have to rely on the charge of the electrons: one can rely on the magnetic moment.

A number of devices have been proposed which make use of magnetic bit cells and yet do not have mechanical parts. They are usually referred to as magnetic random access memories (MRAMs), since they combine the non-volatility of the magnetic memories with the functionalities of the random access memories.

 

The goal of this project is to study one (or more than one) kind of such devices, chosen amongst the most promising for computer applications. Given the multiple choice in the kind of devices to study, the project can be tuned to fit either MPhil or PhD students.

 

The major part of the work is experimental. The research student will be introduced to micro- and nano-fabrication techniques currently used in microelectronic industry. These include, but are not limited to, photolithography, electron-beam lithography and focused ion beam lithography.

PhD students will also be trained in the modeling of spintronic devices through micromagnetic simulations.

 

To apply please send an e-mail containing your CV with a summary of your skills to aruotolo@cityu.edu.hk. In alternative you can directly contact Dr. Ruotolo in the Dept. of Physics and Materials Science, room G6601, lift 2.