17 Jan '17
Experiments conducted by scientists at the Novosibirsk-based Rzhanov Institute of Semiconductor Physics show that new multilayer graphene based flash memory can offer much higher IPS (instructions per second) and data storage time values than in analogs based on other materials.
According to Yuri Novikov, PhD, a senior research fellow at the Institute, the new flash memory is built on a technology of injecting and storing an electrical charge in a data-retaining medium, which is multilayer graphene. Other components of the memory include tunnel and barrier layers; the former is made of silicon oxide while the latter is made of a dielectric material with a high value of permittivity.
Flash memory efficiency (which is revealed in a time period a charge is stored, and also in its IPS value) varies with a work function value of the data-retaining medium. The work function here shows energy that is used to remove an electron from the substance. The multilayer graphene the Siberian researchers have used reportedly demonstrates a high work function value for electrons (about 5eV (electronvolts)), a very important characteristic. Because of that, on the points of contact between multilayer graphene and silicon oxide the potential barrier value is increased to around 4eV. The entire Siberian research has been built around this effect. For comparison, on the points of contact between silicon and silicon oxide the potential barrier value is just 3.1eV. That is why in flash memory based on storing the charge in traditional Si clusters thicker tunnel and barrier layers are used, which inevitably reduces its IPS (capacity).
“As our multilayer graphene based flash memory uses a thin tunnel layer, the IPS value doubles and even triples. In addition, we can use lower reprogramming voltages, with a considerably high work function enabling a longer time of injected charge storage,” Mr. Novikov said.