Significant thermal conductivity reduction of silicon nanowire forests through discrete surface doping of germanium

Abstract

Silicon nanowires (SiNWs) are promising materials for the realization of highly-efficient and cost effective thermoelectric devices. Reduction of the thermal conductivity of such materials is a necessary and viable pathway to achieve sufficiently high thermoelectric efficiencies, which are inversely proportional to the thermal conductivity. In this article, vertically aligned forests of SiNW and germanium (Ge)-doped SiNW with diameters around 100 nm have been fabricated, and their thermal conductivity has been measured. The results show that discrete surface doping of Ge on SiNW arrays can lead to 23% reduction in thermal conductivity at room temperature compared to uncoated SiNWs. Such reduction can be further enhanced to 44% following a thermal annealing step. By analyzing the binding energy changes of Ge-3d and Si-2p using X-ray photoelectron spectroscopy, we demonstrate that surface doped Ge interacts strongly with Si, enhancing phonon scattering at the Si-Ge interface as has also been shown in non-equilibrium molecular dynamics studies of single nanowires. Overall, our results suggest a viable pathway to improve the energy conversion efficiency of nanowire-forest thermoelectric nanomaterials. V C 2015 AIP Publishing LLC.

Band gap opening in stanene induced by patterned B–N doping

“…In the past few years, many studies illustrated that due to doping and some other defects can reduce the thermal conductivity of material. [73][74] Thus, we assume that such B-N co-doping in stanene might lower the thermal conductivity in stanene. Moreover, such BN@stanene can be useful for electronic and optoelectronic devices.…”

Thermal conductivity suppression in GaAs–AlAs core–shell nanowire arrays

“…A comparable reduction has also been observed in Si NW (d ≈ 100 nm) arrays with discrete surface doping of Ge. 31 While GaAs-AlAs systems are most widely utilized in optoelectronics where advanced thermal engineering may facilitate the design of, e.g., improved-efficiency light-emitting diode (LED) CSNWs, 48 our findings are also expected to translate to other III-V systems with thermoelectric potential. For instance, InSb and InAs-based NWs have attracted much interest for thermoelectric applications.…”

“…Such an approach has been applied recently to, e.g., InAs, 18 Bi 2 Te 3 , 26,27 BiSbTe alloy, 28 and Si NWs with various surface modifications. [28][29][30][31][32] The NW growth and sample preparation steps are shown in Fig. 1(a).…”

Optimized Peltier cooling via an array of quantum dots with stair-like ground-state energy configuration

“…There are two major pathways to improve the performance of Peltier coolers (i) decreasing the lattice thermal conductance (ii) enhancing the cooling power via suitable energy filtering techniques. Both of these techniques are widely employed to enhance the performance of thermoelectric generators [1][2][3][4][5][6][7][8][9] and coolers [11][12][13][14][15][16][17][20][21][22][23][24][25].Approaches towards the direction of nanostructuring as well as heterostructuring has so far proven successful in the suppressing phonon mediated lattice thermal conductivity via scattering and confinement of long wavelength phonons [32][33][34][35][36][37][38][39][40][41][42][43]. Hence, in this paper, we focus on optimizing the cooling power without the consideration for lattice thermal conductance.…”