Author: Publisher:
ISBN:
Category : Photovoltaic cells
Languages : en
Pages : 0
Book Description
Atomic-scale Characterization of Hydrogenated Amorphous-silicon Films and Devices
Author: Atomic-scale Characterization of Hydrogenated Amorphous-silicon Films and Devices
Author: Publisher:
ISBN:
Category : Light
Languages : en
Pages : 0
Book Description
Our research is concerned with improving the electronic properties of hydrogenated amorphous silicon (a-Si:H) films and of photovoltaic (PV) cells that use these films. Two approaches toward this goal are being taken. One is to establish the character of silicon particle growth in the rf glow discharges that are used to make the films and PV cells, and to understand the particle incorporation into the films. The ultimate goal of this effort is to find mitigating techniques that minimize the particle incorporation. During this contract period, we have developed a novel particle light-scattering technique that provides a very detailed and sensitive diagnostic of the particles suspended in the discharge, The second program is directed toward measuring the electronic properties of these thin-film PV cells, as a function of depth within the cell. The approach being taken is to use a scanning tunneling microscope to measure the depth-dependent electronic properties of cross-sectioned PV cells. During the present period, cell cleaving and cross-section locating methods, both in a ultrahigh vacuum environment, have been successfully developed.
Atomic-scale Characterization of Hydrogenated Amorphous-silicon Films and Devices
Author: Alan C. GallagherPublisher:
ISBN:
Category : Light
Languages : en
Pages : 18
Book Description
Our research is concerned with improving the electronic properties of hydrogenated amorphous silicon (a-Si:H) films and of photovoltaic (PV) cells that use these films. Two approaches toward this goal are being taken. One is to establish the character of silicon particle growth in the rf glow discharges that are used to make the films and PV cells, and to understand the particle incorporation into the films. The ultimate goal of this effort is to find mitigating techniques that minimize the particle incorporation. During this contract period, we have developed a novel particle light-scattering technique that provides a very detailed and sensitive diagnostic of the particles suspended in the discharge, The second program is directed toward measuring the electronic properties of these thin-film PV cells, as a function of depth within the cell. The approach being taken is to use a scanning tunneling microscope to measure the depth-dependent electronic properties of cross-sectioned PV cells. During the present period, cell cleaving and cross-section locating methods, both in a ultrahigh vacuum environment, have been successfully developed.
Atomic-scale Characterization of Hydrogenated Amorphous-silicon Films and Devices
Author: Alan C. GallagherPublisher:
ISBN:
Category : Light
Languages : en
Pages : 19
Book Description
The research is concerned with improving the electronic properties of hydrogenated amorphous silicon (a-Si:H) films and of photovoltaic (PV) cells that use these films. Two approaches toward this goal are being taken. One is to establish the character of silicon particle growth in the rf glow discharges that are used to make the films and PV cells, and to understand the particle incorporation into the films. The ultimate goal of this effort is to find mitigation techniques that minimize the particle incorporation. During this contract period, we developed a novel particle light-scattering technique that provides a detailed and sensitive diagnostic of small (8-60-nm diameter) particles suspended in the discharge. We used this to measure the particle growth rates and densities, versus conditions in pure-silane discharges. The second program is directed toward measuring the electronic properties of thin-film PV cells, as a function of depth within the cell. The approach being taken is to use a scanning tunneling microscope (STM) to measure the depth-dependent electronic properties of cross-sectioned PV cells. During the present period, measurements on single and tandem amorphous silicon cells have been carried out. Using STM current-voltage spectroscopy, these measurements distinguish the boundaries between the highly conducting and intrinsic layers, and should allow one to deduce the chemical potential versus depth in the cell.
Publications of the National Institute of Standards and Technology ... Catalog
Author: National Institute of Standards and Technology (U.S.)Publisher:
ISBN:
Category :
Languages : en
Pages : 1162
Book Description
Energy Research Abstracts
Author: Growth Mechanisms and Characterization of Hydrogenated Amorphous-silicon-alloy Films. Final Subcontract Report, 15 February 1991--14 April 1994
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This report describes work performed to better understand the atomic-scale structure of glow-discharge-produced a-Si:H, a-Ge:H, and a-Si:Ge:H films; its effect on film quality; and its dependence on deposition discharge conditions. Hydrogenated a-Si films are from a silane rf discharge onto atomically flat crystal Si and GaAs substrates. The substrates are then transferred in a scanning tunneling microscope, where the atomic-scale surface morphology is measured. The films were deposited using device-quality deposition conditions; IR absorption, [sigma][sub L], and [sigma][sub D] indicate high-quality intrinsic films. From the thickness dependence of the surface morphology, we determined that the films initially conform smoothly to an atomically flat Si or GaAs substrate, but as the thickness increases the roughness steadily increases to approximately 10% of the length of the scanned region. The surface of 100--400-nm-thick films is highly inhomogeneous, with steep hills and canyons in some areas and large atomically smooth regions in others. These unexpectedly large surface irregularities indicate severe and often connected void structures in the growing film, as well as relatively limited-range surface diffusion of the incorporating SiH[sub 3] radicals. On the other hand, large atomically flat surface were occasionally found, indicating the possibility of growing a homogeneous and compact amorphous film if appropriate growth conditions could be discovered.
Growth Mechanisms and Characterization of Hydrogenated Amorphous- Silicon-alloy Films. Annual Subcontract Report, 14 February 1991--13 February 1992
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This report describes an apparatus, constructed and tested, that allows measurement of the surface morphology of as-grown hydrogenated amorphous silicon films with atomic resolution using a scanning tunneling microscope. Surface topologies of 100-[degree][Lambda]-thick intrinsic films, deposited on atomically flat, crystalline Si and GaAs, are reported. These films surfaces are relatively flat on the atomic scale, indicating fairly homogeneous, compact initial film growth. The effect of probe-tip size on the observed topology and the development of atomically sharp probes is discussed. 17 refs, 9 figs.
Growth Mechanisms and Characterization of Hydrogenated Amorphous-silicon-alloy Films. Annual Subcontract Report, 14 February 1992--13 February 1993
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This report describes work performed to better understand the atomic-scale structure of glow-discharge-produced a-Si:H, a Ge:H, and a-Si:Ge:H films; its effect on film quality; and its dependence on deposition discharge conditions. Hydrogenated a- Si films are deposited from a silane rf discharge onto atomically flat crystal Si and GaAs substrates. The substrates are then transferred in vacuum to a scanning tunneling microscope, where the atomic-scale surface morphology is measured. The films were deposited at T[sub s] = 30[degree]C and 250[degree]C from a silane rf glow discharge using device-quality deposition conditions of 2.66 Pa (0.5 Torr) silane pressure, 1.7 [Angstrom]/s deposition rate, and small power/flow; IR absorption, [sigma][sub L], and [sigma][sub D] indicate high-quality intrinsic films. From the thickness dependence of the surface morphology, we determined that the films initially conform smoothly to an atomically flat Si or GaAs substrate, but as the thickness increases the roughness steadily increases to approximately 10% of the length of the scanned region. The surface of 100-400-nm-thick films is highly inhomogeneous, with steep hills and canyons in some areas and large atomically smooth regions in others. These unexpectedly large surface irregularities indicate severe and often connected void structures in the growing film, as well as relatively limited-range surface diffusion of the incorporating SiH[sub 3] radicals. On the other hand, large areas of atomically flat surface were occasionally found, indicating the possibility of growing a homogeneous and compact amorphous film if appropriate growth conditions could be discovered.
Growth Mechanisms and Characterization of Hydrogenated Amorphous-silicon-alloy Films
Author: Alan C. GallagherPublisher:
ISBN:
Category : Photovoltaic cells
Languages : en
Pages : 21
Book Description