Tuesday, January 26, 2010

Finding NEMO: French Atomic Agency Discovers New Memory Technology Called Nano Electrochemical MemOries

Scientists at the  Commissariat A l'Energie Atomique ((CEA) Paris, FR) have developed a new memory technology called NEMOs or Nano Electrochemical MemOries. U.S. Patent 7,652,907 describes the  process for manufacturing the layers of a NEMO electrochemical electronic memory cell   

According to inventors Didier Bloch and Frederic Le Cras, the NEMO device is comprised of at least one first active layer capable of reversibly releasing and/or accepting at least one ionic species, at least one second active layer capable of reversibly releasing and/or accepting the ionic species, a solid electrolyte between the first active layer and the second active layer. Current pulse generating means are provided to modify the state of the cell and for measuring the electrochemical potential difference between the first active layer and the second active layer so as to determine the state of the cell.

Nano Electrochemical MemOries may be integrated particularly into a large number of electronic and data processing devices, communication terminals, apparatuses and equipment.

The materials used to implement a NEMO memory device are not toxic, do not require any particular manipulation precautions, are inexpensive and may be manipulated in the ambient atmosphere. They are adapted to thin layer production techniques used in microelectronics.

The electrochemical memory device has low power consumption, high sensitivity and high speed, and good stability of electrodes over time. A NEMO memory cell has good reversibility, and the change from an "ON" state to an "OFF" state and from an "OFF" state to an "ON" state may be provoked by a first current pulse and a second current pulse opposite to the first pulse respectively, or by short circuiting the system.

The first and second  active layers may be based on at least one intercalation compound comprising a transition metal oxide. The intercalation compound may be a lithiated transition metal oxide, for example a lithiated manganese oxide such as LiMn2O4, with a stoichiometric spinel structure. The thickness of the first layer may range between 10 nanometers and 200 nanometers, or at least less than 1000 nm.

A layer or a stack of layers forming an electrolyte separates the first active layer from the second active layer. The electrolyte may be formed from an ionic conducting and electronic insulating material, for example a "Lipon®" type glass with composition 1B2O3-0.8Li2O-0.8Li2SO4. The thickness of the electrolyte is chosen so that it is resistant to the passage of electrons, but is sufficiently weak so that it does not create any excessive resistance to the passage of ions. The thickness of the electrolyte layer may for example be between nanometers and nanometers, and may for example be of the order of nanometers. Two current collector layers may be associated with each active layer.

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