Ankit Bhardwaj PPT
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This document discusses the fabrication of porous silicon samples at different current densities and their characterization and application in sensing. Porous silicon was fabricated by anodizing silicon wafers in HF and DMF solutions at current densities ranging from 10 to 50 mA/cm2. SEM images showed that pore size increased with higher current density. Photoluminescence and Raman spectroscopy indicated shifts related to quantum confinement effects. Different functional groups were detected using FTIR. The porous silicon samples showed sensitivity to ethanol vapors for capacitive sensing applications. Future work is proposed to further optimize the porous silicon for vapor sensing.
Ankit Bhardwaj PPT
- 2. CONTENTS • OBJECTIVE • MATERIAL USED • THEORY • FABRICATION OF POROUS SILICON • CHARACTERIZATION • APPLICATION IN SENSING • CONCLUSION • FUTURE PERSPECTIVE
- 3. OBJECTIVE FABRICATION OF POROUS SILICON EFFECT ON PORE SIZE WITH INCREASING THE CURRENT DENSITY CHARACTERIZATION OF POROUS SILICON SAMPLES SENSING APPLICATION OF POROUS SILICON
- 4. MATERIAL USED • SILICON WAFER • PLATINUM ELECTRODE , ALUMINIUM PLATE • ETHANOL , ACETONE AND DI WATER • AMMONIUM HYDROXIDE, HYDROGEN PEROXIDE • 10% HF SOLUTION, DIMETHYLE FLUORIDE, N-PENTANE • HYDROCHLORIC ACID, SULPHURIC ACID, SILVER PASTE • 1 TEFLON TWEEZER, 2 ROUND BOTTLES, 4 BEAKERS, DROPPER, PAINT BRUSH ,HEATER,SENSING SETUP
- 5. THEORY • POROUS SILICON FIRST DEVELOPED IN 1956 BY UHLIR • SILICON IS THE MOST DOMINANT MATERIAL USED FOR MICROELECTRONIC DEVICE. • CRYSTALLINE SILICON IN ITS BULK APPEARANCE IS COMMONLY NOT TAKENIN TO CONSIDERATION AS OPTICAL , MECHANICAL OR BIO MEDICAL MATERIAL. • BUT WHEN THE DIMENSIONS ARE DOWNSCALED THE PROPERTIES ARE CHANGED DRASTICALLY. • LIGHT EMITTING PROPERTIES OCCUR DUE TO QUANTUM CONFINEMENT. • POROUS SILICON IS INTERESTING FOR OPTICAL APPLICATIONS DUE TO ITS POROSITY.
- 6. FABRICATION OF POROUS SILICON
- 7. We have used 5 Silicon Wafer of Diameter: 3” + 0.02” Orientation: <100> Thickness: 350-406 µm Type: P (Boron doped)
- 8. PRE-CLEANING Rinse the sample with DI water Boiling(56.3 C)-Silicon wafer in acetone Rinse with DI water and treatment with ethanol(5min) Rinse with DI water Cleaning Heating in NH4OH: H2O2: DI water at (1:1:5 at 70c for 10min) Rinse with DI water Dipping for 10min in 3:1 H2SO4 and H202 Rinse with DI water Dipping in 10% HF solution Rinse with DI water Heating for 10min at 75c H2O :H2O2 :HCL (6:1:1) Dip in 10% HF solution Rinse with DI water Rinse with DI water Dry
- 9. ETCHING • Two electrodes are needed to maintain charge neutrality and to complete the circuit. • Two reactions are occurring simultaneously , the anode(oxidation) reaction and cathode(reduction) reaction. • Cathode is made up of Platinum wire. • Anode is of Aluminum Plate mount with Porous sample. • A constant current is passed between cathode and anode immersed in HF and DMF(1:3 ratio). Fig. Etching set-up in our laboratory
- 10. SETUP THEORY
- 11. Mechanism Of Pore Formation-
- 12. SAMPLE NAME SAMPLE IMAGE AFTER ETCHING ETCHING PARAMETERS A Current Density = 10 mA/cm2 Etching Time = 40 minutes Electrolyte Conc. (HF:DMF) = 1:3 Current = 0.011304A B Current Density = 20 mA/cm2 Etching Time = 40 minutes Electrolyte Conc. (HF:DMF) = 1:3 Current = 0.022608A C Current Density = 30 mA/cm2 Etching Time = 40 minutes Electrolyte Conc. (HF:DMF) = 1:3 Current = 0.033912A D Current Density = 40 mA/cm2 Etching Time = 40 minutes Electrolyte Conc. (HF:DMF) = 1:3 Current = 0.044216A E Current Density = 50 mA/cm2 Etching Time = 40 minutes Electrolyte Conc. (HF:DMF) = 1:3 Current = 0.05652A
- 13. Sample Name E versus T Graphs A B C D E
- 14. CHARACTERIZATION
- 15. SCANNING ELECTRON MICROSCOPY Sample A- Current Density = 10 mA/cm2
- 16. Sample B- Current Density = 20mA/cm2
- 17. Sample C- Current Density = 30 mA/cm2
- 18. Sample D- Current Density = 40 mA/cm2
- 19. Sample E- Current Density = 50 mA/cm2
- 20. SEM ANALYSIS Sample No. Current Density,J Etching Time ( Minutes ) Etching Concentration HF:DMF Diameterof Pores (µm) Sample A JA= 10mA/cm2 40 1:3 1.331 Sample B JB= 20mA/cm2 40 1:3 1.427 Sample C JC= 30mA/cm2 40 1:3 1.952 Sample D JD= 40mA/cm2 40 1:3 2.524 Sample E JE= 50mA/cm2 40 1:3 3.217
- 21. PL SPECTROSCOPY Sample Name Current density (mA/cm2) PL peak (eV) A 10 1.72 B 20 1.78 C 30 1.86 D 40 1.93 E 50 1.98
- 22. RAMAN SPECTROSCOPY Sample Name Current density (mA/cm2) Wavenumber (cm-1) A 10 519.5 B 20 518.7 C 30 517.9 D 40 517.1 E 50 516.4
- 23. FTIR SPECTROSCOPY Wave number 615 769 1281 Bonding Si-O-Si C-Cl -CH2X SAMPLE A SAMPLE B Wave number 509 830 1256 1506 Bonding C-Br C-Cl CH2X N-O
- 24. CONTINUE…….. SAMPLE C Wavenumber 615 840 1275 1506 Bonds Si-O-Si C-Cl C-N N-O Wave number 840 1257 1525 1859 2621 Bonds C-Cl C-N N-O CH2X O-H SAMPLE D
- 26. APPLICATION IN SENSING Sensing setup Fabricated Sensor of Sample A
- 27. Capacitive Sensing Response Sensitivity Graph MaximumCapacitance PPM
- 28. CONCLUSION • SEM IMAGES SHOWS THAT PORE SIZE INCREASE WITH INCREASE IN CURRENT DENSITY. • PHOTOLUMINESCENCE PEAK SHIFTED TOWARDS RIGHT (BLUE SHIFT). • RAMAN SPECTRA SHIFTED TOWARDS LEFT (RED SHIFT). • FTIR SPECTRA SHOWS VARIOUS TYPE OF BONDS ON PS SURFACE AT DIFFERENT CURRENT DENSITY. • POROUS SILICON SAMPLE PREPARED IS SENSITIVE TO ETHANOL VAPOR.
- 29. FUTURE PERSPECTIVE • WE WILL PREPARE THE POROUSSILICON AT DIFFERENT HF CONCENTRATIONS AND ETCHING TIME. • WE WILL DO COMPARATIVE STUDY WITH DIFFERENT ORGANIC SOLVENT SUCH AS DIMETHYLFORMAMIDE(DMF), DIMETHYLSULFOXIDE(DMSO) AND ACETONITRILE (MECN). • WE WILL DO COMPARATIVE STUDIES OF P-TYPE AND N-TYPE SILICON WAFER. • WE WILL FIND THE SENSITIVITY, RESPONSE TIME, RECOVERY TIME ETC. FOR DIFFERENT SAMPLES UNDER DIFFERENT CONDITIONS AS MENTIONED ABOVE AND COMPARE THESE PARAMETERS TO GET THE EFFICIENT SENSOR FROM THEM. • WE WILL CHARACTERIZE THE DIFFERENT SAMPLES UNDER DIFFERENT CONDITIONS AS MENTIONED ABOVE AND COMPARE THEM ALL IN TERMS OF SURFACE MORPHOLOGY, STRUCTURE MORPHOLOGY, RAMAN PEAKS AND PL ETC.