Mr. Ghosh,

Rather you need DRS.

Defects can cause changes in absorption, for example a color center, or defects in NiOx. The energy of the absorption event or change in refractive index or other interaction with light related to that defect might tell you something about the energy of the defect relative to the ground state, but I think you will need to couple another technique to UV-Vis-NIR if you want any kind of structural information.

I agree with Daniel above - you can detect *some* defects and even find out about their transition energy (by using quantum-mechanical simulations, you can estimate what kind of defects you are dealing with, but that is a non-straightforward method). You can also detect some microstructural issues, such as surface porosity (non-flat spectral baseline if the pores are of a size comparable with the used wavelength). Apart from that, there is very little information to give for such a generally-phrased question.

Will you explain it @Dr. Ivanova?

Dear Daniel and Jarosz,

Your answers are helpful. It is known that in case of doping/ defect formation, band gap of material may change. The band gap can be calculated from Tauc plot. But, I'm not asking the effects of the defects. I am asking that can we track the defect related transitions of a material from the UV-Vis-NIR spectroscopy only?

Measure the Urbach energy from absorption data. The value of Urbach energy tells about disorder in materials.

Will you elaborately explain it for my convenience? @Chandra Bhal Singh

UV-VIS can show the absorption. But the defect related peak broadening can see precisely in PL characterization .

Mr. Bablu K. Ghosh, as you have mentioned, 'defect related peak broadening can see precisely in PL characterization ' is true. But, my clear question is that, can UV-Vis spectroscopy give any preliminary signature about those defects?

I agree with Daniel above

As Chandra said if you want to compare several samples, you can compare the intensity of the impurity absorption which position is after Urbach energy in UV-Vis spectroscopy.

How can we calculate the Urbach energy from UV-Vis spectroscopy?

According to Urbach rule the absorption edge in the spectral range of direct optical transition has exponential shape a = ao exp (E/Eu) .

From this article you can know the calculation procedure for Urbach energy.

Conference Paper Effect of boron doping on optical and electrical properties ...

Your answer is pretty helpful @Chandra Bhal Singh for the calculation of Urbach energy. Also, in the conference paper that you have supplied, it is written that 'Increase in Urbach energy indicates the enhancement of defects in films with increase of boron concentration'. Can you give me any journal citation for this quotation? It will be very much helpful for me.

UV-Vis - IT spectroscopies open the great possibilities to investigate the optically active defects in many materials.

For me, UV and VIS photo- and cathodolumunescence have been the most.important methods to investigate cubic boron nitride. It is analogue of diamond

Hello Anupam,

Please read this paper

Article Urbach edge of crystalline and amorphous silicon: a personal review

Usually defects on materials such as porosity or roughness will definitely modify the UV-Vis curve and, therefore, the absorption coefficient and bandgap. Besides the transmittance spectra (if your material is not completely opaque), you could use an integration sphere to gather the diffused light from reflectance measurements. Then, you could apply a numerical method (e.g. Denton's method) to calculate the absorption coefficient. Although ellipsometry would also be an option, data interpretation may be a little bit more complex.

See the following references and supporting information for more details:

Article Ultrafast Epitaxial Growth Kinetics in Functional Oxide Thin...

Article Ultraviolet pulsed laser crystallization of Ba0.8Sr0.2TiO3 f...

Article Laser-induced metal organic decomposition for Ce0.9Zr0.1O2−y...

Article Ultrafast Crystallization of Ce 0.9 Zr 0.1 O 2– y Epitaxial ...

Article Growth of ferroelectric Ba0.8Sr0.2TiO3 epitaxial films by ul...

http://hdl.handle.net/10803/286006

Dear Anupam Ghosh ,

Due to defects in materials, the materials UV-Visible data will show blue shift. If you compare UV-Visible data of bulk and defect created materials, there will be clear blue shift, from lower wavelength to higher wavelength.

Attached paper will be helpful.

This shift may also be from blue to red. It depend on your material's defect shape and source. I am attaching here both article, showing different effects.

Also you can test HRTEM, the material will show different lattice fringes at normal site and defect site. Many article are avail about this.

Article Porous defect-modified graphitic carbon nitride via a facile...

Article Photoassisted Construction of Holey Defective g-C 3 N 4 Phot...

you can use following papers:

Urbach edge of crystalline and amorphous silicon: a personal review

Laser-induced metal organic decomposition for Ce0.9Zr0.1O2−y epitaxial thin film growth

use DRS

Your answer was pretty helpful Chandra Bhal Singh.

Muhammad Asim Khan, the papers provided by you are also somehow related to my question. Thanks.

After lot of useful discussion on this topic, I want to say that UV-Vis-NIR spectra can give information about the presence of defects. These defcts may be generated either by addition of some impurity or by the irradiation of samples by any ionizing radiation. The changes in the spectra will be observed in the form of shift in the position of original peak or in the change in the intensity of peaks. However exact peak generated due to defects can be obtained from difference spectra of sample before and after irradiation. FTIR spectra as well as difference spectra also can provide sufficient information about defects.

J. of Luminescence 130 447 (2010)

J. Non Crystalline Solids 357 3757 (2011)

Ind. J. Pure and Appl. Phys. 55 775 (2017)