Bismuth selenide(Bi2Se3)belongs to the(Bi,Sb)2(Se,Te)3 family,which has been long known as excellent thermoelectric materials.Recently,various Bi2Se3 nanostructures including nanowires and nanoribbons have been synthesized,which enable new opportunities to enhance thermoelectric efficiencies through thermal conductivity reduction.In this work,we report on thermoelectric properties characterization of individual Bi2Se3 nanoribbons with the suspended-microdevice method [1].First,the intrinsic thermal conductivities of Bi2Se3 nanoribbons with different thicknesses and widths are measured through multiple measurements of the same sample with different suspended lengths to eliminate the effects of contact thermal resistance between the nanoribbon and the membranes [2].Our results show that intrinsic thermal conductivities of Bi2Se3 nanoribbons are at least 50%lower than the values of the bulk Bi2Se3 in the entire temperature range from 20 K to 320 K and the temperature of the peak thermal conductivity is shifted from 10 K (for bulk Bi2Se3 [3])to~50K(for Bi2Se3 nanoribbons)indicating enhanced phonon-boundary scattering.On the other hand,it is shown that thermal conductivities of Bi2Se3 nanoribbons depend on both the thickness and the width and thus the Casimir length has been used to interpret thermal conductivities of different nanoribbons.Moreover,thermoelectric properties of individual Bi2Se3 nanoribbons have been concurrently characterized with a four-probe suspended microdevice and the maximum thermoelectric figure of merit is found to be 0.17 at 320 K.