Benjamin Gesemann | Martin-Luther-Universität Halle-Wittenberg (original) (raw)
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Papers by Benjamin Gesemann
Data Revues 16310748 V16i1 S1631074812000987, Jan 3, 2013
Data Revues 16310748 Unassign S1631074812000987, Jun 15, 2012
Wehrspohn/Photon Management in Solar Cells, 2015
ABSTRACT The name "black silicon" refers to all randomly structured silicon int... more ABSTRACT The name "black silicon" refers to all randomly structured silicon interfaces with lateral feature sizes in the submicron range and aspect ratios (structure height/lateral feature size) larger than one. There are a variety of possibilities to achieve a black silicon structure at the silicon interface. From a historical point of view the development is a result of integrated circuit technologies, especially the structuring of silicon by plasma and dry etching processes. Reactive ion etching (RIE) processes seem to be promising candidates for the structuring of solar cells. The structure evolution of black silicon under repeated pulsed laser irradiation can be understood as an interference effect. The light trapping properties of the investigated black silicon structures depend strongly on the feature size of the structures. As a result of the excellent light trapping, high short-circuit currents are a common property of almost all cell concepts.
Active Photonic Materials IV, 2011
Periodic silicon nanostructures can be used for different kinds of gas sensors depending on the a... more Periodic silicon nanostructures can be used for different kinds of gas sensors depending on the analyte concentration. First we present an optical gas sensor based on the classical non-dispersive infrared technique for ppm-concentration using ultra-compact photonic crystal gas cells 1 . It is conceptually based on low group velocities inside a photonic crystal gas cell and anti-reflection layers coupling light into the device. Experimentally, an enhancement of the CO 2 infrared absorption by a factor of 2.6 to 3.5 as compared to an empty cell, due to slow light inside a 2D silicon photonic crystal gas cell, was observed; this is in excellent agreement with numerical simulations. In addition we report on silicon nanotip arrays 2 , suitable for gas ionization in ion mobility microspectrometers (micro-IMS) having detection ranges in principle down to the ppt-range. Such instruments allow the detection of explosives, chemical warfare agents, and illicit drugs, e.g., at airports. We describe the fabrication process of large-scale-ordered nanotips with different tip shapes. Both silicon microstructures have been fabricated by photoelectrochemical etching of silicon.
Photonic Crystal Materials and Devices VIII, 2008
2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013
Renewable Energy and the Environment, 2013
Photonics and Nanostructures - Fundamentals and Applications, 2010
We present measurements of the thermal emission properties of 2D and 3D silicon photonic crystals... more We present measurements of the thermal emission properties of 2D and 3D silicon photonic crystals with and without substrate heated resistively as well as passively with an aluminium hotplate. The out-of-plane and in-plane emission properties were recorded and compared to numerical simulation. It turned out that for the in-plane 2D photonic crystal and out-of-plane 3D photonic crystal emission a photonic stop gap effect is visible. For the out-of-plane 2D photonic crystal emission, no photonic bandgap effect is observable but instead strong silicon oxide emission from native oxide inside the pores of silicon are observable. A model for the modified thermal emission is presented. #
Comptes Rendus Chimie, 2013
The sensitivity of optical gas sensors depends on the length of interaction between detected radi... more The sensitivity of optical gas sensors depends on the length of interaction between detected radiation and the gas under investigation. A reduction in cell size of the sensor generally results in reduced sensitivity. Photonic crystals possess certain regions of their photonic band structure which offer low group velocities. Making use of these effects, smallervery compact -gas sensors should be possible. Problems to solve with numerical calculations are the identification of the operating point in relation to the photonic bandstructure and selection of an appropriate photonic crystal, the calculation of transmission through the photonic structure with and without the gas inside the sensor cell and the determination of an optimized anti-reflection-layer to improve the air-sensorinterface, since the low group velocity results in a high reflectivity.
IEEE Transactions on Nanotechnology, 2000
The 9/11 events have led to an increase in the request for sensors and sensor systems that can de... more The 9/11 events have led to an increase in the request for sensors and sensor systems that can detect rapidly, efficiently, and at moderate cost trace explosives and a whole range of toxic substances at diverse control points, e.g., at airports and inside air conditioning systems in aircraft and public buildings. To date, the security screening instruments of choice are ion mobility spectrometers (IMS), which are basically time-of-flight mass spectrometers (Sielemann, 1999 and Stach, 1997). Such instruments allow for the detection of explosives, chemical warfare agents, and illicit drugs. Widespread adoption of the IMS technology in civilian security screening applications, for instance, at airports, has been hindered due to the fact that state-of-the-art spectrometers employ radioactive ion sources. We report on fabrication and measurements of large-scale-ordered silicon nanotip arrays, used to replace the radioactive source for IMS gas ionization. Surface ionization mechanisms on the platinum-coated silicon surface can be significantly increased compared to flat structures due to the strong field enhancement at the tips. We will show measurements of the ion current of planar surfaces compared to microstructured surfaces as well as a photoelectrochemical etching process that allows to etch flat tips with a low aspect ratio as well as long tips with high aspect ratios with exact control about the tip profile.
Data Revues 16310748 V16i1 S1631074812000987, Jan 3, 2013
Data Revues 16310748 Unassign S1631074812000987, Jun 15, 2012
Wehrspohn/Photon Management in Solar Cells, 2015
ABSTRACT The name "black silicon" refers to all randomly structured silicon int... more ABSTRACT The name "black silicon" refers to all randomly structured silicon interfaces with lateral feature sizes in the submicron range and aspect ratios (structure height/lateral feature size) larger than one. There are a variety of possibilities to achieve a black silicon structure at the silicon interface. From a historical point of view the development is a result of integrated circuit technologies, especially the structuring of silicon by plasma and dry etching processes. Reactive ion etching (RIE) processes seem to be promising candidates for the structuring of solar cells. The structure evolution of black silicon under repeated pulsed laser irradiation can be understood as an interference effect. The light trapping properties of the investigated black silicon structures depend strongly on the feature size of the structures. As a result of the excellent light trapping, high short-circuit currents are a common property of almost all cell concepts.
Active Photonic Materials IV, 2011
Periodic silicon nanostructures can be used for different kinds of gas sensors depending on the a... more Periodic silicon nanostructures can be used for different kinds of gas sensors depending on the analyte concentration. First we present an optical gas sensor based on the classical non-dispersive infrared technique for ppm-concentration using ultra-compact photonic crystal gas cells 1 . It is conceptually based on low group velocities inside a photonic crystal gas cell and anti-reflection layers coupling light into the device. Experimentally, an enhancement of the CO 2 infrared absorption by a factor of 2.6 to 3.5 as compared to an empty cell, due to slow light inside a 2D silicon photonic crystal gas cell, was observed; this is in excellent agreement with numerical simulations. In addition we report on silicon nanotip arrays 2 , suitable for gas ionization in ion mobility microspectrometers (micro-IMS) having detection ranges in principle down to the ppt-range. Such instruments allow the detection of explosives, chemical warfare agents, and illicit drugs, e.g., at airports. We describe the fabrication process of large-scale-ordered nanotips with different tip shapes. Both silicon microstructures have been fabricated by photoelectrochemical etching of silicon.
Photonic Crystal Materials and Devices VIII, 2008
2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013
Renewable Energy and the Environment, 2013
Photonics and Nanostructures - Fundamentals and Applications, 2010
We present measurements of the thermal emission properties of 2D and 3D silicon photonic crystals... more We present measurements of the thermal emission properties of 2D and 3D silicon photonic crystals with and without substrate heated resistively as well as passively with an aluminium hotplate. The out-of-plane and in-plane emission properties were recorded and compared to numerical simulation. It turned out that for the in-plane 2D photonic crystal and out-of-plane 3D photonic crystal emission a photonic stop gap effect is visible. For the out-of-plane 2D photonic crystal emission, no photonic bandgap effect is observable but instead strong silicon oxide emission from native oxide inside the pores of silicon are observable. A model for the modified thermal emission is presented. #
Comptes Rendus Chimie, 2013
The sensitivity of optical gas sensors depends on the length of interaction between detected radi... more The sensitivity of optical gas sensors depends on the length of interaction between detected radiation and the gas under investigation. A reduction in cell size of the sensor generally results in reduced sensitivity. Photonic crystals possess certain regions of their photonic band structure which offer low group velocities. Making use of these effects, smallervery compact -gas sensors should be possible. Problems to solve with numerical calculations are the identification of the operating point in relation to the photonic bandstructure and selection of an appropriate photonic crystal, the calculation of transmission through the photonic structure with and without the gas inside the sensor cell and the determination of an optimized anti-reflection-layer to improve the air-sensorinterface, since the low group velocity results in a high reflectivity.
IEEE Transactions on Nanotechnology, 2000
The 9/11 events have led to an increase in the request for sensors and sensor systems that can de... more The 9/11 events have led to an increase in the request for sensors and sensor systems that can detect rapidly, efficiently, and at moderate cost trace explosives and a whole range of toxic substances at diverse control points, e.g., at airports and inside air conditioning systems in aircraft and public buildings. To date, the security screening instruments of choice are ion mobility spectrometers (IMS), which are basically time-of-flight mass spectrometers (Sielemann, 1999 and Stach, 1997). Such instruments allow for the detection of explosives, chemical warfare agents, and illicit drugs. Widespread adoption of the IMS technology in civilian security screening applications, for instance, at airports, has been hindered due to the fact that state-of-the-art spectrometers employ radioactive ion sources. We report on fabrication and measurements of large-scale-ordered silicon nanotip arrays, used to replace the radioactive source for IMS gas ionization. Surface ionization mechanisms on the platinum-coated silicon surface can be significantly increased compared to flat structures due to the strong field enhancement at the tips. We will show measurements of the ion current of planar surfaces compared to microstructured surfaces as well as a photoelectrochemical etching process that allows to etch flat tips with a low aspect ratio as well as long tips with high aspect ratios with exact control about the tip profile.