Electronic properties of doped silicon nanocrystal films

Abstract

The structural and electrical properties before and after laser annealing of spin-coated films of doped silicon nanocrystals (ncs) produced from the gas phase are presented. While the as-deposited films form a porous network of ncs and show only weak electrical conductivity independent of the doping level, a laser annealing step leads to sintering and melting of the particles and tremendously increases the lateral conductivity. By controlled doping of the initial particles, the conductivity can be further enhanced by seven orders of magnitude reaching values of up to 5 Ω−1 cm−1. The conductivity is found to increase with the doping concentration for highly doped samples while it is independent of the doping level below a critical concentration of 1019 cm−3. The results are discussed within a compensational model taking into account the defect concentration from electron paramagnetic resonance measurements and the activation energies of the electrical conductivity. Surface segregation of phosphorus during growth is identified as the origin of the apparently small phosphorus doping efficiency.

Formation of high conductive nano-crystalline silicon embedded in amorphous silicon-carbide films with large optical band gap

“…It is also found that the Si 2p peak can be decomposed into two sub-bands, which is assigned to Si-Si state (E BSi2p =99.6±0.1 eV) and Si-C state (E BSi2p =100.4±0.1 eV), respectively. 15 It is suggested from XPS spectra that the most of Si atoms are bonded to neighboring Si and only small portion of Si are bonded to C atoms. It is noted that the Si/C ratio is almost the same for un-doped and P-doped samples even after thermal annealing.…”

“…13,14 Lechner et al fabricated the doped nc-Si films and they obtained the maximum conductivity up to about 5 S/cm with the very small conductivity activation energy. 15 From the view point of device application, it is highly desired to get nc-Si:SiC films with high conductivity at the suitable optical band gap (>2.5 eV) so that they can act as the window layer or the conductive layer in nano-crystalline SiC film-based optoelectronic devices without absorbing incident (or emitted) light too much. 13,16 In our previous work, hydrogenated amorphous silicon carbide (a-SiC:H) films were prepared in a plasma-enhanced chemical vapor deposition (PECVD) system.…”

A Combined Ion Implantation/Nanosecond Laser Irradiation Approach towards Si Nanostructures Doping

“…Si NCs embedded in SiO 2 are widely investigated for their novel size-dependent electronic and optoelectronic properties [6][7][8][9][10][11][12][13]. In particular, the exploitation of the properties of such systems in real devices demands an accurate control of their doping.…”

“…Doping of semiconductor nanostructures has proven to be distinct from the corresponding bulk materials [1][2][3][4][5] and recently great attention has been focused on developing practical methodologies to dope and control the doping properties of Si nanostructures such, as nanoclusters (NCs) [6][7][8][9][10][11][12][13] and nanowires [14][15][16][17], and on developing theoretical approaches to understand these properties [18][19][20][21][22][23]. The control of doping properties of Si nanostructures allows the fabrication of complex nanomaterials characterized by unpreceded electrical and optoelectronic functionalities.…”

Spontaneous Generation of Electromotive Force in Thin Film Al/Nanosilicon/Al Structures

“…The use of annealing to increase the conductivity of nc-Si films was already known [21,22]. Possible mechanisms include sintering, particle transfer, and even sublimation of nanoparticles from a hot substrate to a cold one [23].…”