Thermoelectric properties of Indium doped skutterudite thick film synthesized by a facile technique of electrochemical deposition

Doped/filled skutterudites are much studied materials due to their excellent thermoelectric performance.However,their synthesis and preparation is complicated.This work synthesized indium(In)doped cobalt triantimonide(CoSb_(3))skutterudite thick films using a facile electrochemical deposition technique through chronoamperometric steps for 2 h.The nominal composition of In element is found in the range of 0.55e0.23 for a stoichiometric condition of In doped CoSb_(3)thick films.The early crystal growth of In doped films shows instantaneous nucleation and is controlled by the charge transfer process with diffusion coefficient,D of 10^(-5)cm^(2)/s.The incorporation of In into the interstitial sites of CoSb_(3)cages is evident from the lattice constant(a)expansion as observed in XRD.The optimum Seeback coefficient(S)of the 0.5 mmol In doped CoSb_(3)thick film is89.84 mV/K at 282 K,due to an increase in the carrier concentration(n~10^(20)cm^(-3)).The negative S is due to the electron donor behaviour of the In.Meanwhile,high electrical conductivity,s value(14.26 kS/m)contributes to a power factor(S2s)increment of 115.11 mW/(m$K2).The result shows a promising thermoelectric property of doped skutterudite synthesized by electrochemical deposition technique.

Microfabrication of functional polyimide films and microstructures for flexible MEMS applications

Polyimides are widely used in the MEMS and flexible electronics fields due to their combined physicochemical properties,including high thermal stability,mechanical strength,and chemical resistance values.In the past decade,rapid progress has been made in the microfabrication of polyimides.However,enabling technologies,such as laser-induced graphene on polyimide,photosensitive polyimide micropatterning,and 3D polyimide microstructure assembly,have not been reviewed from the perspective of polyimide microfabrication.The aims of this review are to systematically discuss polyimide microfabrication techniques,which cover flm formation,material conversion,micropatterning,3D microfabrication,and their applications.With an emphasis on polyimide-based flexible MEMS devices,we discuss the remaining technological challenges in polyimide fabrication and possible technological innovations in this field.

Mechanically strengthened graphene-Cu composite with reduced thermal expansion towards interconnect applications

High-density integration technologies with copper(Cu)through-silicon via(TSV)have emerged as viable alternatives for achieving the requisite integration densities for the portable electronics and micro-electro-mechanical systems(MEMSs)package.However,significant thermo-mechanical stresses can be introduced in integrated structures during the manufacturing process due to mismatches of thermal expansion and the mechanical properties between Cu and silicon(Si).The high-density integration demands an interconnection material with a strong mechanical strength and small thermal expansion mismatch.In this study,a novel electroplating method is developed for the synthesis of a graphene-copper(G-Cu)composite with electrochemically exfoliated graphenes.The fabrication and evaluation of the G-Cu composite microstructures,including the microcantilevers and micromirrors supported by the composite,are reported.We evaluated not only the micromechanical properties of the G-Cu composite based on in-situ mechanical resonant frequency measurements using a laser Doppler vibrometer but also the coefficients of thermal expansion(CTE)of the composite based on curvature radius measurements at a temperature range of 20–200℃.The Young’s modulus and shear modulus of the composite are approximately 123 and 51 GPa,which are 1.25 times greater and 1.22 times greater,respectively,than those of pure Cu due to the reinforcement of graphene.The G-Cu composite exhibits a 23%lower CTE than Cu without sacrificing electrical conductivity.These results show that the mechanically strengthened G-Cu composite with reduced thermal expansion is an ideal and reliable interconnection material instead of Cu for complex integration structures.