Paramagnetic Defects in Undoped Microcrystalline Silicon Deposited by the Hot-Wire Technique

Abstract

We report on a study of ESR and conductivity on a series of hot-wire CVD microcrystalline silicon samples prepared with different hydrogen dilution of silane. We observe two different types of dangling bond defects in ESR in different microscopic environments. One type of defect is located at outer surfaces accessible to oxygen and/or chemicals, the other is located at inner boundaries presumably at columnar structures. We correlate changes of the defect density induced by either annealing, exposure to air or wet-chemical treatment with the morphology and electronic properties of the films. We find that annealing at 200 °C induces irreversible changes in donor concentration as monitored by an ESR signal at g = 1.9981±3.

Stability of microcrystalline silicon for thin film solar cell applications

“…The results show similarities with the findings reported earlier [13,17,20]. Differences in the observations could be due to the different material preparation and different experimental conditions and should not be over interpreted at this point.…”

“…The fact that the increase of N S after annealing in O 2 or air can be restored with an HF dip indicates that this is a surface process. Similar conclusions are presented in [17].…”

“…There have only been a few investigations on recently prepared material [16][17][18][19][20]. In the present paper we will discuss the results of some of the phenomena for material and solar cells prepared by PECVD or HWCVD and compare these results with earlier investigations.…”

Recombination in μc-Si:H pin solar cells

“…The fact that T C is slightly higher in the solar cell than in the film is related to a different position of the Fermi level in the two materials. T C is determined by details of the deposition process and the quality of the absorber material [8]. Note that we do not observe an EDMR signal at g ¼ 2:0043 in the pin cell.…”

Postdeposition thermal annealing and material stability of 75 °C hydrogenated nanocrystalline silicon plasma-enhanced chemical vapor deposition films

“…1 This stems from its higher carrier mobility, higher doping efficiency, and enhanced infrared ͑IR͒ absorption compared with hydrogenated amorphous silicon ͑a-Si:H͒. 6,[8][9][10][11] The detailed microscopic mechanisms re-sponsible for these effects are not yet clear. In films with high-crystalline volume fraction, the grains aggregate into a porous columnarlike structure making the film surface and grain boundaries very sensitive to oxygen and/or water vapor absorbed from the atmosphere, to potentially undermine the electronic transport properties.…”