Systems and methods for light absorption and field emission using microstructured silicon

Abstract

Methods and systems for absorbing infrared light, and for emitting current are described. A sample, such as a sample containing mainly silicon, is microstructured by at least one laser pulse to produce cone-like structures on the exposed surface. Such microstructuring enhances the infrared absorbing, and current emission properties of the sample.

1 - 58 . (canceled) 
     
     
         59 . A method of emitting electrons from a sample, comprising
 structuring a surface of a semiconductor sample by applying a plurality of radiation pulses thereto, and   applying an electric field to the structured sample so as to cause the sample to emit an electric current.   
     
     
         60 . The method of  claim 59 , wherein said radiation pulses have a duration less than about 500 femtoseconds. 
     
     
         61 . The method of  claim 59 , wherein said radiation pulses have a duration less than about 150 femtoseconds 
     
     
         62 . The method of  claim 59 , wherein said radiation pulses have a wavelength of about 800 nm. 
     
     
         63 . The method of  claim 60 , wherein said pulses have a fluence of at least about 2 kJ/m 2 . 
     
     
         64 . The method of  claim 63 , wherein said pulses have a fluence in a range of about 2 kJ/m 2  to about 30 kJ/m 2 . 
     
     
         65 . The method of  claim 59 , wherein the step of applying radiation pulses to the sample surface is performed in the presence of a background gas. 
     
     
         66 . The method of  claim 65 , wherein said background gas comprises any of nitrogen, air, or a halogenic gas. 
     
     
         67 . The method of  claim 59 , wherein said structuring step comprises generating a plurality of microstructures on said surface. 
     
     
         68 . The method of  claim 67 , wherein said microstructures comprise a plurality of microstructured spikes. 
     
     
         69 . The method of  claim 59 , wherein said structuring step further comprises generating a plurality of nanometer-scale particles disposed on said surface. 
     
     
         70 . The method of  claim 59 , wherein said semiconductor sample comprises any of silicon, germanium or indium phosphide. 
     
     
         71 . The method of  claim 68 , wherein said microstructured spikes exhibit a number density in a range of about 7.5×10 −3  to about 4×10 −2  per square micrometer. 
     
     
         72 . The method of  claim 59 , wherein said structured sample is characterized by a turn-on field that is less than about 10 V/μm. 
     
     
         73 . The method of  claim 72 , wherein said structured sample is characterized by a threshold field that is less than about 20 V/μm. 
     
     
         74 . The method of  claim 72 , wherein said turn-on field is less than about 1.4 V/μm. 
     
     
         75 . The method of  claim 73 , wherein said threshold field is less than about 2.2 V/μm. 
     
     
         76 . The method of  claim 59 , further comprising applying said emitted current to a luminescent material to cause luminescence thereof. 
     
     
         77 . The method of  claim 59 , further comprising applying said emitted current to a screen containing a luminescent material. 
     
     
         78 . The method of  claim 77 , further comprising selectively applying said emitted current to portions of the screen so as to cause formation of an image via luminescence of said luminescent material. 
     
     
         79 . A method of generating an emitted electric current, comprising providing a semiconductor sample characterized by a turn-on field of less than about 10 V/μm, and
 applying an electric field to the sample so as to cause the sample to emit an electric current.   
     
     
         80 . The method of  claim 79 , wherein said sample is characterized by a threshold field of less than about 20 V/μm. 
     
     
         81 . The method of  claim 79 , wherein said semiconductor sample comprises any of silicon, germanium or indium phosphide. 
     
     
         82 . A system for emitting an electric current, comprising
 a semiconductor sample characterized by a turn-on field that is less than about 10 V/μm,   an electric field generator for applying an electric field to the sample so as to cause the sample to emit an electric current, and   a load for receiving said electric current and generating a signal in response to said received electric current.   
     
     
         83 . The system of  claim 82 , wherein said sample is further characterized by having a threshold field that is less than about 20 V/μm. 
     
     
         84 . The system of  claim 82 , wherein said load luminesces in response to said received electric current. 
     
     
         85 . The system of  claim 82 , wherein said load is suitable for use in at least one of a display, a microwave source, a mass spectrometer, a pressure sensor, an acoustic intensity sensor, and a displacement sensor. 
     
     
         86 . The system of  claim 85 , wherein the display includes at least one of a cathode-ray display and a panel display. 
     
     
         87 . The system of  claim 82 , wherein said sample comprises a plurality of microstructures on a surface thereof. 
     
     
         88 . A method of generating luminescence radiation, comprising
 applying a plurality of radiation pulses to a silicon sample in the presence of a background gas so as to generate a plurality of luminescence states in the sample, and causing said silicon sample to luminescence.   
     
     
         89 . The method of  claim 88 , wherein said background gas comprises any of oxygen or air. 
     
     
         90 . The method of  claim 88 , wherein said radiation pulses have a duration less than about 500 femtoseconds. 
     
     
         91 . The method of  claim 90 , wherein said radiation pulses have a fluence in a range of about 2.5 kJ/m to about 30 kJ/m. 
     
     
         92 . The method of  claim 88 , wherein the step of causing the sample to luminesce comprises exposing the sample to electromagnetic radiation so as to cause it to luminesce. 
     
     
         93 . The method of  claim 88 , further comprising annealing said silicon sample subsequent to application of the radiation pulses at an elevated temperature. 
     
     
         94 . The method of  claim 93 , wherein said annealing step is performed at a temperature of about 1300 K. 
     
     
         95 . The method of  claim 93 , wherein said annealing step is performed for a duration in a range of about 30 minutes to about 5 hours.