8:00 x-intercept you have found is not the true value, as y=0 line lies little bit above the horizontal axis of the graph. So Eg has to be slightly bigger than 2.8 eV. Moreover, the use of "Quick fit" tool is the right and practical way for linear fitting. It gives you two parameters slope (m) and y-intercept (y0) of the fitting line. Then, calculation of x-intercept (so of Eg) is straightforward: x0=-y0/m.
The estimated band gap in your video around 8:23 should be a little bigger. The y-axis does not start at 0 and thus the fitted line reaches lower value on x-axis than it should. What do you think?
Respected Sir in the PL band gap limitation section point No # that indirect band gap do not possess luminescence but they thermally loose energy. My material is quasi band gap can I measure the band gap and it will be correct as I already corelate the band gap with the Urbach Energy and Tolerance factor
Regarding your query about the limitation of indirect band gaps in the PL band gap section, it is indeed true that indirect band gap materials typically do not exhibit significant luminescence, as they tend to lose energy thermally. However, it is important to note that your material, which possesses a quasi-band gap, may exhibit different characteristics compared to indirect band gap materials. In the case of quasi-band gap materials, it is possible to measure the band gap and obtain accurate results. You mentioned that you have already correlated the band gap with the Urbach Energy and Tolerance Factor, which indicates that you have taken into account relevant parameters to support the accuracy of your measurements. It would be advisable to conduct further research and review relevant literature to ensure that the methods you have employed for measuring the band gap in quasi-band gap materials align with established practices and principles in the field. This will help to validate your findings and provide a more comprehensive understanding of the band gap energy in your specific material.
WoA, What I have understood from your message is that you need the following videos th-cam.com/video/ZyNKITpA3wA/w-d-xo.html th-cam.com/video/JwhhfSqwqVE/w-d-xo.html
In the literature, you'll find many references. However, please note that it strictly depend on the nature of materials. You may have a look to the below refs; www.researchgate.net/post/What-is-the-relationship-among-Photoluminescene-intensity-surface-states-and-crystallinity www.nature.com/articles/srep02657 (contrary for this material)
Thanks for your video, really helpful :) I have a silly question: during the PL measurement that I watched (a direct bandgap material), the laser beam is constantly on the sample, constantly providing energy to the material. In this case, why electrons relax? In my mind they would only relax and emit photons when the laser beam would no longer be reaching the sample...
Thanks for the appreciation dear. The thing you're talking about is the procedure of UV-Vis and not PL. In PL, a sample is excited at a specific wavelength and then its emission is scanned in a defined region. Thanks
@@SAYPhysics I see. I agree with that :) That's actually how the experiment I watched happened (it was actually micro-PL). Still I can't understand why there is relaxation once the laser is not turned off during the experiment...
@Beatriz de Simoni As I see it, it's not necessary that every photon do excitation (through resonance mechanism), some even cause de-excitations through stimulations. Thanks
In photoluminescence spectroscopy, excitation wavelength is the wavelength at which we excite the sample, while the detector observes its emission as emission intensity. This is PL, not UV vis data. Thanks
Another point in indirect bandgap. Phonons are not emitted. Phonons are excited and the phonon momentum in addition to photon energy is necessary to excite electron from VBM to CB.
Incorrect way to describe fluorescence or phosphorescence. It is not the illumination time that differentiates PL. It the response time of the system in which electron transition time from CBM or metastable state to VBM determined if it is fluo or phos.
This was amazing, thank you so much. You were a great help!
Thanks for the appreciation dear
Thanks for this great presentation
Thanks for the appreciation dear 😊
8:00 x-intercept you have found is not the true value, as y=0 line lies little bit above the horizontal axis of the graph. So Eg has to be slightly bigger than 2.8 eV. Moreover, the use of "Quick fit" tool is the right and practical way for linear fitting. It gives you two parameters slope (m) and y-intercept (y0) of the fitting line. Then, calculation of x-intercept (so of Eg) is straightforward: x0=-y0/m.
Yes, you're right dear. Thanks for your valuable input.
@@SAYPhysics You're welcome. Thanks for videos.
The estimated band gap in your video around 8:23 should be a little bigger. The y-axis does not start at 0 and thus the fitted line reaches lower value on x-axis than it should. What do you think?
Yes, you're right. I should have been calculated at y=0, as explained in the first session of the tutorial. Please check the pinned comment. Thanks
Respected Sir in the PL band gap limitation section point No # that indirect band gap do not possess luminescence but they thermally loose energy. My material is quasi band gap can I measure the band gap and it will be correct as I already corelate the band gap with the Urbach Energy and Tolerance factor
Regarding your query about the limitation of indirect band gaps in the PL band gap section, it is indeed true that indirect band gap materials typically do not exhibit significant luminescence, as they tend to lose energy thermally. However, it is important to note that your material, which possesses a quasi-band gap, may exhibit different characteristics compared to indirect band gap materials.
In the case of quasi-band gap materials, it is possible to measure the band gap and obtain accurate results. You mentioned that you have already correlated the band gap with the Urbach Energy and Tolerance Factor, which indicates that you have taken into account relevant parameters to support the accuracy of your measurements.
It would be advisable to conduct further research and review relevant literature to ensure that the methods you have employed for measuring the band gap in quasi-band gap materials align with established practices and principles in the field. This will help to validate your findings and provide a more comprehensive understanding of the band gap energy in your specific material.
@@SAYPhysics Thank you Sir
Excellent video!
Thanks dear 😊
Very Well explained.
Thanks dear
Aoa sir . Kindly tell how we get numerical data which we export into the origion for the plot and which software is used for such calculation?
WoA, What I have understood from your message is that you need the following videos
th-cam.com/video/ZyNKITpA3wA/w-d-xo.html
th-cam.com/video/JwhhfSqwqVE/w-d-xo.html
Sir I am talking about the CIF file which is exported into origion for plotting graph
@@78691414 I think you yet mean imported into Origin not exported. Here's the video th-cam.com/video/r1EKRfV4ZRg/w-d-xo.html
Sorry imported
One more question, how we get XRD/machine data & which software is used to get such data.
Great Sir!👍👍👍
Thanks dear
hello, thanks for the nice presentation. Do you have any reference for point 8 in slide "photoluminescence process"?
In the literature, you'll find many references. However, please note that it strictly depend on the nature of materials. You may have a look to the below refs;
www.researchgate.net/post/What-is-the-relationship-among-Photoluminescene-intensity-surface-states-and-crystallinity
www.nature.com/articles/srep02657 (contrary for this material)
Thank you so much
You're welcome dear
Dr SB, can we take the average value of excitation and emission, which comes exactly 2.8 eV..
It's not necessary. May be in one case as an exception, but can't be generalized. Thanks
@@SAYPhysics Thanks Dr SB..
Hello Doctor.
I need a phone number that contains WhatsApp or Telegram for the purpose of inquiries from you
@@happymanhappy308 sayphysics@gmail.com
Thanks
Thanks for your video, really helpful :) I have a silly question: during the PL measurement that I watched (a direct bandgap material), the laser beam is constantly on the sample, constantly providing energy to the material. In this case, why electrons relax? In my mind they would only relax and emit photons when the laser beam would no longer be reaching the sample...
Thanks for the appreciation dear. The thing you're talking about is the procedure of UV-Vis and not PL. In PL, a sample is excited at a specific wavelength and then its emission is scanned in a defined region. Thanks
@@SAYPhysics I see. I agree with that :) That's actually how the experiment I watched happened (it was actually micro-PL). Still I can't understand why there is relaxation once the laser is not turned off during the experiment...
@Beatriz de Simoni As I see it, it's not necessary that every photon do excitation (through resonance mechanism), some even cause de-excitations through stimulations. Thanks
@@SAYPhysics thanks a lot for answering!
You're welcome
excitation intensity and emission intensity calculate kesay ki kahan sy aye ye bta dain ?
In photoluminescence spectroscopy, excitation wavelength is the wavelength at which we excite the sample, while the detector observes its emission as emission intensity. This is PL, not UV vis data. Thanks
Another point in indirect bandgap. Phonons are not emitted. Phonons are excited and the phonon momentum in addition to photon energy is necessary to excite electron from VBM to CB.
Yes, you're right. Thanks for the input. The attached references are discussing the same thing.
Incorrect way to describe fluorescence or phosphorescence. It is not the illumination time that differentiates PL. It the response time of the system in which electron transition time from CBM or metastable state to VBM determined if it is fluo or phos.
Yes, it is the emission features that result in the luminescence. Thanks for the input
🌹
Thanks dear
Qm lectures ?
In a month IA. Thanks