As dimensions of nanoelectronic devices become smaller, CPU hot spots become increasingly more difficult to manage. Applying mechanical strain in nanostructures provides an additional tuning mechanism for both electronic band structures and phonon dispersions that is independent of other methods such as alloying and dimensional confinement. By breaking crystal symmetry, strain increases anisotropy.
We present thermal conductivity calculations, performed in thin Si and Ge strained films, using first principles calculations of vibrational frequencies under biaxial strain, along with a phonon Boltzmann transport equation within the relaxation time approximation. We find that, while in-plane transport is not strongly dependent on strain, the cross-plane component of the thermal conductivity tensor shows a clear strain dependence, with up to 20% increase (decrease) at 4% compressive (tensile) strain in both Si and Ge. We also uncover that strain emphasizes the anisotropy between in-plane and cross-plane thermal conductivity across several orders of magnitude in film thickness. Read the article in J. Appl. Phys. here: http://dx.doi.org/10.1063/1.4971269
We fabricate, measure, and simulate ultrathin diamond membranes with large lateral dimensions for MALDI TOF MS of high-mass proteins. With a minimal thickness of 100 nm and cross sections of up to 400×400 μm sq., the membranes offer extreme aspect ratios. Ion detection is demonstrated in MALDI TOF analysis over a broad range from insulin to albumin. The resulting data and simulations show much enhanced resolution as compared to existing detectors, which can offer better sensitivity and overall performance in resolving protein masses.
The article is available in Physical Review Applied: https://doi.org/10.1103/PhysRevApplied.6.064031