Accession Number : AD1039963


Title :   A Micro-Raman Study of Exfoliated Few-Layered n-Type Bi2Te2.7Se0.3 (Postprint)


Descriptive Note : Journal Article - Open Access


Corporate Author : CLEMSON UNIV SC CLEMSON United States


Personal Author(s) : Liu,Fengjiao ; Hu,Longyu ; Karakaya,Mehmet ; Puneet,Pooja ; Podila,Ramakrishna ; Bhattacharya,Sriparna ; Rao,Apparao M ; Rao,Rahul


Full Text : http://www.dtic.mil/dtic/tr/fulltext/u2/1039963.pdf


Report Date : 28 Nov 2017


Pagination or Media Count : 24


Abstract : Previously we showed that the thermoelectric (TE) performance of bulk n-type Bi2Te2.7Se0.3 can be enhanced by subjecting it to a combined process of chemical or mechanical exfoliation (C/ME) followed by a rapid densification and restacking of the exfoliated layers via the spark-plasma-sintering technique (SPS). Here, we present a systematic micro-Raman study of two-dimensional flakes of n-type Bi2Te2.7Se0.3 produced by the C/ME process, as a function of the flake thickness. We found Raman evidence for flakes with: (i) integer number of quintuples which exhibited a strong electron-phonon coupling, and (ii) non-integer number of quintuples, or sub-quintuples which exhibited the forbidden IR active mode due to symmetry lowering. Detailed atomic force microscopy was used to confirm the number of quintuples in all flakes examined in this study. The restacking and densification of these flakes by SPS promoted the formation of charged grain boundaries, which led to the enhanced TE properties via the energy filtering process.


Descriptors :   materials , crystal structure , transport properties , scattering , electrons , electrical conductivity , grain boundaries , charge carriers , thermal conductivity , raman spectra


Distribution Statement : APPROVED FOR PUBLIC RELEASE