The quest for novel low-dissipation devices is one of the most critical for the future of semiconductor technology and nano-systems. The development of a low-power, universal memory will enable a new paradigm of non-volatile computation. Here we consider STT-RAM as one of the emerging candidates for low-power non-volatile memory. We show different configurations for STT memory and demonstrate strategies to optimize key performance parameters such as switching current and energy. The energy and scaling limits of STT-RAM are discussed, leading us to argue that alternative writing mechanisms may be required to achieve ultralow power dissipation, a necessary condition for direct integration with CMOS at the gate level for non-volatile logic purposes. As an example, we discuss the use of the giant spin Hall effect as a possible alternative to induce magnetization reversal in magnetic tunnel junctions using pure spin currents. Further, we concentrate on magnetoelectric effects, where electric fields are used instead of spin-polarized currents to manipulate the nanomagnets, as another candidate solution to address the challenges of energy efficiency and density. The possibility of an electric-field-controlled magnetoelectric RAM as a promising candidate for ultralow-power non-volatile memory is discussed in the light of experimental data demonstrating voltage-induced switching of the magnetization and reorientation of the magnetic easy axis by electric fields in nanomagnets.
We theoretically investigated electron and phonon
transport in a quantum superlattice and evaluated a possible
thermoelectric figure of merit increase. The presented model
takes into account electron and phonon transport modifications
due to the space confinement caused by the mismatch in
electronic and thermal properties between dot and host
materials. The numerical calculations were carried out for a
structure that consists of multiple layers of Si with
regimented quantum dots separated by wetting layers and
spacers. Transport coefficients (electric conductivity, Seebeck
coefficient and lattice thermal conductivity) were calculated as
functions of quantum dot volume fraction for different dot
sizes. It is shown that additional thermoelectric figure of
merit enhancement due to the presence of quantum dots may be
obtained. The predicted enhancement is mostly due to the
significant drop in the lattice thermal conductivity caused by
the acoustic phonon scattering by quantum dots.
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