Boltzmann transport equation-based thermal modeling approaches for hotspots in microelectronics

Fourier diffusion has been found to be inadequate for the prediction of heat conduction in modern microelectronics, where extreme miniaturization has led to feature sizes in the sub-micron range. Over the past decade, the phonon Boltzmann transport equation (BTE) in the relaxation time approximation has been employed to make thermal predictions in dielectrics and semiconductors at micro-scales and nano-scales. This paper presents a review of the BTE-based solution methods widely employed in the literature and recently developed by the authors. First, the solution approaches based on the gray formulation of the BTE are presented. The semi-gray approach, moments of the Boltzmann equation, the lattice Boltzmann approach, and the ballistic-diffusive approximation are also discussed. Models which incorporate greater details of phonon dispersion are also presented. Hotspot self-heating in sub-micron SOI transistors and transient electrostatic discharge in NMOS transistors are also examined. Results, which illustrate the differences between some of these models reveal the importance of developing models that incorporate substantial details of phonon physics. The impact of boundary conditions on thermal predictions is also investigated.     

Topological signature of deterministic chaos in short nonstationary signals from an optical parametric oscillator

Although deterministic chaos has been predicted to occur in the triply resonant optical parametric oscillator (TROPO) 15 years ago, experimental evidence of chaotic behavior in this system has been lacking so far, in marked contrast with most nonlinear systems, where chaos has been actively tracked and found. This situation is probably linked to the high sensitivity of the TROPO to perturbations, which adversely affects stationary operation at high power. We report the experimental observation in this system of a burst of irregular behavior of duration 80 micros. Although the system is highly nonstationary over this time interval, a topological analysis allows us to extract a clear-cut signature of deterministic chaos from a time series segment of only nine base cycles (3 micros). This result suggests that nonstationarity is not necessarily an obstacle to the characterization of chaos.     

General formulation for proton decay rate in minimal supersymmetric SO(10) GUT

We give an explicit formula for the proton decay rate in the minimal renormalizable supersymmetric (SUSY) SO(10) model. In this model, the Higgs fields consist of the 10 and SO(10) representations in the Yukawa interactions with matter and of the 10, , 126, and 210 representations in the Higgs potential. We present all the mass matrices for the Higgs fields contained in this minimal SUSY SO(10) model. Finally, we discuss the threshold effects of these Higgs fields on the gauge coupling unification.Received: 8 March 2005, Published online: 8 June 2005PACS: 12.10.-g, 12.10.Dm, 12.10.Kt     

Ground state of the quasi-1D correlated electronic system BaVS3

In this paper we review the salient features of the different instabilities exhibited by the quasi-1D system BaVS₃ and show that there is a subtle interplay between the different phases stabilized. The analysis of the Peierls instability shows that the mobile dz² electrons are more localized than calculated because of their strong correlation with the localized e(t_2g) electrons. The complex AF magnetic structure of BaVS₃ incorporates the magnetization of the e(t_2g) electrons with the Peierls pairing of the dz² electrons into magnetic singlets. Finally, we propose that the zig-zag disorder remaining after an incomplete orthorhombic phase transition could change the sign of the magnetic coupling and thus help to stabilize the canted ferromagnetism observed in non stoichiometric BaVS_3−δ and Sr and Ba substituted compounds.