Nanoporous SiCOH/CxHy dual phase films with an ultralow dielectric constant and a high Young's modulus

Understanding Bulk Defects in Topological Insulators from Nuclear‐Spin Interactions

“…[6][7][8][9][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] The type of conduction in the Tetradymite family of TIs is strongly related to the type of structural defects present (anion vacancies or antisite). [1][2][3][4][5][6][7][8][9][10][11][12][13][14]16,22,25,28,32,35] Bi 2 Te 3 crystals grown from stoichiometric melts are p-type due to the presence of large number of Bi Te antisite defects. The type of conduction may be adjusted through fine tuning of the non-stoichiometry of the Bi/Te ratio, i.e., to dope the system by generating antisite defects of Bi Te (p-type) or Te Bi (n-type [18] ).…”

“…[20][21][22][26][27][28][29] Recently, an effort aimed at improving the TE efficiency (figure of merit parameter, ZT) concluded that Bi 2 Te 3 -Sb 2 Te 3 solid solutions yield improved TE materials, according to the ZT parameter, which is maximized in the case of Bi 0.5 Sb 1.5 Te 3 [7,[17][18][19][20][24][25][26][27][28][29] Other ternary telluride compounds in the same class as these layered materials, Bi 2 Te 2 Se and Bi 2 Te 2 S, have shown the potential of tuning and enhancing transport properties. [1][2][3][4][5][6]30,32] The discovery of topological insulators has changed the way we look at chalcogenides. [11][12][13][14][15][16] An ideal TI has a bulk interior characterized by an insulating band gap, while the boundary exhibits gapless Dirac-like edge (2D-TIs) or surface states (3D-TIs).…”

“…The observation of metallic surface states often requires minimal bulk defects or compensation for the free carriers. [1][2][3][4][5][6]11,14,37,[38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] Novel properties have been predicted, such as quantum-Hall-like behavior with quantized conductance of charge and spin in the absence of a magnetic field, and dissipation-less quantum Hall states with time-reversal symmetry (TRS). [11][12][13][14][15][16] First-principles calculations [3,15,16,33,[36][37][38][39][40]48,49,51] and Angle Resolved Photoemission Spectroscopy (ARPES) [5,11,12,39,40,…”

“…[11] To date, electrical transport measurements, scanning tunneling microscopy (STM) and ARPES have been the main workhorses for the study of surface states. [1][2][3][4][5][6]11,13,40,41,42,43] These techniques work best with high-quality thin films (<20 nm) [40][41][42][43] or large single crystals and at low temperatures (<30 K). [1][2][3][4][5][6]11,39,42,43] There is, however, a need for characterizing materials at room temperature or materials of suboptimal quality.…”

“…[1][2][3][4][5][6]11,13,40,41,42,43] These techniques work best with high-quality thin films (<20 nm) [40][41][42][43] or large single crystals and at low temperatures (<30 K). [1][2][3][4][5][6]11,39,42,43] There is, however, a need for characterizing materials at room temperature or materials of suboptimal quality. To this end, nuclear magnetic resonance (NMR) has been proposed as a tool to characterize TI properties.…”