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Window Coating Absorbance Spectra

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Presentation on theme: "Window Coating Absorbance Spectra"— Presentation transcript:

1 Window Coating Absorbance Spectra
Lisa Pawlowicz 17 August 2010

2 Overview Materials and Methods Absorbance of Substrates
Absorbance due to In2O3 (ITO) Absorbance due to MgO Topics for Further Investigation

3 Window Coatings 1.22” diameter 50 Å MgO 45 Å In2O3 (ITO)
.098” Borofloat (Sn doped on one side) .098” Fused Silica OR 45 Å In2O3 (ITO) 50 Å MgO Windows cut by Oswald Siegmund at SSL Coatings applied by Joe Libera at Argonne coatings applied to one side but (likely) diffused onto both

4 Absorbance Spectrum Scans
Absorbance scans done with a Hitachi U-3010 spectrophotometer: A - absorbance I0 – intensity of incident light I – intensity of transmitted light α – attenuation coefficient x – optical path length (thickness) T - transmission Measuring absolute absorbance: no scaling factor Instrument Parameters Measurement Type: Wavelength Scan Starting Wavelength: nm Ending Wavelength: nm Scan Speed: 300 nm/min Sampling Interval: 1.00 nm High Resolution Path Length: 2.0 mm (window thickness 2.5 mm)

5 Absorbance of Substrate: 7980-2G Fused Silica
, Absorbance of Substrate: G Fused Silica Absorbance Wavelength

6 Absorbance of Substrate: Borofloat
, Absorbance of Substrate: Borofloat Absorbance Wavelength Wavelength

7 Absorbance of Substrates
, Absorbance of Substrates ---- Fused Silica ---- Borofloat Absorbance Wavelength Conclusions: caution required in UV range (Borofloat particularly a poor choice for wavelengths < 350 nm) otherwise these substrates acceptable for the purposes of the LAPPD

8 Absorbance due to ITO Multiple orientations of fused silica due to orientation dependent absorbance of coated window ---- Fused Silica (orientation #1) ---- Fused Silica (orientation #2) ---- Borofloat Absorbance Wavelength

9 Absorbance due to ITO Transmission
no industry standard for ITO coatings Conclusions: ITO absorbance independent of substrate

10 Absorbance due to MgO ---- Fused Silica (orientation #1)
---- Borofloat Absorbance Wavelength

11 Absorbance due to MgO ---- Fused Silica (orientation #1)
---- Borofloat Absorbance Wavelength

12 Transmission Spectrum of
Absorbance due to MgO Transmission Spectrum of 1 nm thick MgO Transmission Bhattacharya, P., Das, R. R., and Katiyara, R. S. (2003). “Fabrication of stable wide-band-gap ZnOÕMgO multilayer thin films.” Applied Physics Letters, 83;

13 Absorbance due to MgO peaks transitions across band gap
---- Fused Silica (orientation #1) ---- Fused Silica (orientation #2) peaks transitions across band gap Absorbance Energy

14 Absorbance due to MgO 1 5-7 eV peak predicted by band structure
caused by interaction with substrate? ITO? could enable unwanted interactions between conduction bands of adjacent layers e- EC EF EV Glass MgO Photocathode 1 Leone, R.M. (2006). Wide band gap engineering of magnesium oxide-zinc oxide II-VI semiconductors (Master’s dissertation, Northern Arizona University, 2006).

15 Absorbance due to MgO 1 5-7 eV peak predicted by band structure
caused by interaction with substrate? ITO? could enable unwanted interactions between conduction bands of adjacent layers EC EF EV e- Glass MgO Photocathode 1 Leone, R.M. (2006). Wide band gap engineering of magnesium oxide-zinc oxide II-VI semiconductors (Master’s dissertation, Northern Arizona University, 2006).

16 Absorbance due to MgO Conclusions:
MgO absorbance doesn’t match literature MgO absorbance shows some dependence on substrate Orientation dependence  implies uneven coating Spectroscopic measurements necessary to ensure quality of samples Interactions between layers could cause complications

17 Topics for Further Investigation
Why is there a 2.75 eV peak in the MgO absorbance spectrum? How do the 5 eV and 2.75 eV peaks in the MgO absorbance spectrum affect MgO’s functionality? How would tempering the different materials affect their absorbance spectra? How do absorbance spectra differ between batches of windows and films?


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