Research On The Thermal Conductivity Of GeTe Nanowire

Phase change memory(PCM),a promising candidate for the next generation memories,has excellent properties such as fast switch,radioresistance and constant scaling of cells' size,which has received extensive attention in recent years.But its commercialization is severely limited by thermal crosstalk between adjacent cells in nanoscale.As a key parameter to characterize the thermal properties of materials,the thermal conductivity directly affects the performance of PCM,therefore,it is particularly important and necessary to thoroughly investigate the thermal conductivity and heat transfer mechanism of one-dimensional nano-scale phase change materials.However,blocked by test errors from blackbody radiation and technical difficulties in preparing suspended samples,researches on the thermal properties of phase-change nanowire materials are extremely rare,correspondingly,impeding the invistagation into the heat transport mechanism.Considering these plights,this paper is mainly focused on the thermal conductivity and heat transfer mechanism in GeTe nanowire,which is a typical phase change material in PCM.In this paper,we report a Nano-3? thermal conductivity measurement theory and method for one-dimensional nano-materials with nanowires attached to substrates and exposed to the atmospheric environment that is compatible with CMOS technology.Under this designed measurement structure,we strictly demonstrate the effect of heat dissipation through the surroundings,and effectively reduce errors based on the unsteady harmonic frequency method.Consequently,this method significantly improves the accuracy of measurement results,and more importantly,provides an approach to studying the thermal conductivity of phase-change nanowire materials in PCM.A series of GeTe nanowires are prepared by specific CMOS processes,and an extremely low thermal conductivity of 0.082 W/(m·K)is obtained by Nano-3? method.Then the size effect of thermal conductivity in nanoscale is investigated to demonstrate the feasibility of control thermal crosstalk in PCM.Subsequently,the phonons' behaviors and heat transport in the nanoscale GeTe material are studied in aspects of phonon modes mismatch,phonon modes' density decrease,phonon localization and phonon group velocity reduction by the ab-initio calculation.Through the experiment and simulation,we make a comprehensive explanation to the mechanism of the size effect for thermal conductivity in nanoscale germanium tel uride materials.