Optical and photoelectric properties of TlInS2 layered single crystals

doi:10.1016/j.cap.2008.02.011

Current Applied Physics

Volume 9, Issue 2, March 2009, Pages 311-316

https://doi.org/10.1016/j.cap.2008.02.011 Get rights and content

Abstract

Single crystals of the layered compound TlInS₂ were grown by direct synthesis of their constituents. The spectral and optical parameters have been determined using spectrophotometric measurements of transmittance and reflectance in the wavelength range 200–2500 nm. Absorption spectra of thin layers of TlInS₂ crystals are used to study the energy gap and the interband transitions of the compound in the energy region 2–2.4 eV. The dispersion curve of the refractive index shows an anomalous dispersion in the absorption region and a normal one in the transmitted region. The direct and indirect band gaps were determined to be 2.34 and 2.258 eV, respectively. Photoconductivity measurements at room temperature resolve the structure that can be identified with the optical transition.

Introduction

TlInS₂ belongs to the interesting group $A^{III} B^{III} C_{2}^{VI}$ of chalcogenide semiconductors and considered one of the highly anisotropic crystals whose properties have recently become the subject of extensive research [1], [2], [3]. Members of this group of crystals, designated with the chemical formula TlBX₂ (where B = In or Ga, X = S, Se or Te) are known as thallium dichalcogenide. They have both layered (TlGaS₂, TlGaSe₂, TlInS₂) and chain (TlInSe₂, TlInTe₂, TlGaTe₂) structures [4].

At room temperature, TlInS₂ belongs to the monoclinic system with space group C₂/c and is arranged in the form of layered structure with a 1:1 ratio of InS:TlS. The lattice of TlInS₂ consists of alternating two-dimensional layers parallel to the (0 0 1) plane with each successive layer turned through a right angle with respect to the preceding layer [5]. The fundamental structural unit of a layer is the In₄S₁₀ polyhedron representing a combination of four elementary InS₄ tetrahedra linked together by bridging S atoms. The combination of the In₄S₁₀ polyhedra into a layer results in trigonal prismatic voids where Tl atoms are located. Tl atoms form nearly planar chains along the [1 1 0] and $[1 \bar{1} 0]$ directions. Hence the number of layers within the unit cell is more than one [6], [7].

This paper reports the results on the optical properties of TlInS₂ layered single crystal in the wavelength range 200–2500 nm. Furthermore, the photoelectric properties at room temperature are studied. As a result of this study we calculated all the optical parameters and energy gap of this sample. To the best of the author’s, the data presented in this work have not been reported before.

Section snippets

Materials and sample preparation

TlInS₂ some material was synthesized by fusing the constituent elements of a stoichiometric proportions into evacuated silica ampoules with a tip at the bottom. All the starting materials used were of extra pure elements (99.999%). To prevent the ampoule from exploding, it was heated in a temperature gradient furnace, so that the sulphur condensed at the cold end and slowly reacted with the heated elements at the hot end. After complete reaction, the ampoule was kept at 1173 K for 10 h to ensure

Optical properties

Transmission measurements were used to determine the absorption coefficient of this compound. Averaging over multiple reflection effects, the values of transmission are given by [9], [28] $T = (1 - R)^{2} \exp (- α d),$ $α = (\frac{1}{d}) \ln [(1 - R)^{2} / 2 T + \sqrt{((\frac{(1 - R)^{4}}{4 T^{2}}) + R^{2})}],$ where R and α are the reflectivity (R is 0.2605 [10]) and the optical absorption coefficient, respectively, and d is the thickness of the sample. At normal incidence the refractive index (n) is given by [9], [28] $n = \frac{(1 + R)}{(1 - R)} + \sqrt{((\frac{4 R}{(1 - R)^{2}}) - k^{2})},$ $k = α λ / 4 π,$ where k is the

Conclusion

Optical and photoelectric properties of TlInS₂ layered single crystal of thickness 0.35 mm were studied. In the optical studies, the direct $(E_{g}^{d})$ and indirect $(E_{g}^{ind})$ energy gaps were determined to be 2.34 and 2.258 eV, respectively. In addition, the phonon energy (E_phonon) and the width of the tail (E_e) to be 26 and 108 meV, respectively. The refractive index showed an anomalous dispersion in the absorption region as well as normal one in the transparent region. From the analysis of dispersion

References (28)

M.P. Hanias et al.
Mater. Res. Bull.
(1992)
S.B. Youssef
Physica A
(1995)
Ke. Tanaka
Thin Solid Films
(1980)
M.M. El-Nahass et al.
Opt. Laser Technol.
(2003)
M.G. Sandoval-Paz et al.
Thin Solid Films
(2005)
R. Yoosuf et al.
Solar Energy Mater. Solar Cells
(2005)
K.R. Allakhverdiev
Solid State Commun.
(1999)
A.M. Bakry et al.
Thin Solid Films
(2000)
K.R. Allakhvediev et al.
J. Phys. Condens. Mat.
(2003)
B. Abay et al.
J. Appl. Phys.
(1998)

K.A. Yee et al.

J. Am. Chem. Soc.

(1991)

D. Müller et al.

Allg. Chem.

(1978)

A. Aydinli et al.

Semicond. Sci. Technol.

(1999)

S.B. Vakhrushev et al.

JETP Lett.

(1984)

Cited by (29)

Preparation of TlInSe<inf>2</inf> thin films using substrate temperature: Characterization, optical and electrical properties
2022, Optical Materials
Chalcogenide materials are very applicable materials that have been utilized in different fields of industry such as photovoltaic, fuel cell, battery, and sensor. Here, we report the fabrication, structure, optical, and DC electrical properties of TlInSe₂ thin films with different thicknesses (195, 229, and 365 nm). The structural properties have been studied using XRD and AFM. The results showed that the prepared films are polycrystalline in the Tetragonal system and that the crystalline size increases with the increase of the film's thickness. The lattice indices of TlInSe₂ and the inter-planar spacing for each diffraction peak have been calculated. The linear and nonlinear optical parameters have been determined using spectrophotometric measurements in the wavelength range of 200–2500 nm. It is found that the direct energy gap ( $E_{g}^{d})$ , the indirect energy gap ( $E_{g}^{i n d})$ , and the phonon energy ( $E_{p h}$ ) are 1.89, 1.61, and 0.025 eV, respectively. The electrical conductivity measurements were also made for TlInSe₂ films of different thicknesses and at temperatures in the range of 30–140 °C. The finding results for our fabricated thin films qualify them for employment in optoelectronic applications.
Structural and optical properties of thermally annealed thallium indium disulfide thin films
2020, Thin Solid Films
Citation Excerpt :
In another study, at room temperature direct and indirect band gap of the crystal were specified as 2.47 eV and 2.27 eV, respectively [17]. TlInS2 single crystal that has monoclinic unit cell has been studied for its structural [14], electrical [18], photoconductive [5, 20] properties. In Ref. [19], the variation of the indirect band gap energy and impurity levels of TlInS2 crystal with thickness were studied.
Structural and optical properties of thallium indium disulfide (TlInS₂) thin films, deposited by thermal evaporation technique and thermally annealed at different temperatures, were analyzed. Crystallite size, dislocation density and lattice strain of the thin films were found from X-ray diffraction experiments. The atomic compositions of the films were determined from energy dispersive spectroscopy analysis. Surface morphology of the films was analyzed using atomic force microscopy. From room temperature transmittance spectrum, the band gap energies of the films were identified. The decrease in band gap energies of the films with the annealing temperature up to 300 ˚C was observed due to increase in crystallite size and decrease in lattice strain. From Raman measurements, it was observed that the Raman shifts of the films were well correlated with those of TlInS₂ bulk crystal.
Temperature and frequency dependence outline of DC electrical conductivity, dielectric constants, and AC electrical conductivity in nanostructured TlInS<inf>2</inf> thin films
2019, Physica E: Low-Dimensional Systems and Nanostructures
Citation Excerpt :
El-Nahass et al. have studied the photoconductivity of TlInS2 single crystals and they have showed that both the dark and photocurrent increase linearly with the applied voltage. The observed photocurrent was higher than that of the dark current, which termed as positive photoconductivity [11]. Exploring chalcogenides thin films for technology applications was delayed until the 2000s, because of the absence of suitable and efficient deposition techniques as well as due to health concerns.
Recently, chalcogenides materials that containing sulfur, S, have attracted scientists attention for using as active recording films in programmable metallization cell memory (PMC) devices. Thus, in the present work a nanostructured TlInS₂ thin film is prepared by using thermal evaporation and is characterized via X-ray diffractometer (XRD) and transmission electron microscope (TEM). Based on XRD calculations and TEM micrograph, the as-deposited thin film shows nanostructure of average particle size equals to 50 ± 4 nm. Subsequently, a device of the structure Au/TlInS₂/Au is fabricated using thermal evaporation and is investigated by using impedance spectroscopy. The DC electrical conductivity is carried out in the temperature range of 358–468 K. The AC electrical and dielectric properties are measured in the dark conditions and their dependence on the temperature (373–473 K) and the frequency (0.5–200 kHz) is discussed. Of these, the σ_ac increases as the temperature increases and it obeys the universal power law σ_ac = Aω^s. Also, the dielectric constants show high values at high temperatures due to the presence of interface charges that is formed at the interfacial surface between the gold electrode and TlInS₂ NPs. Moreover, the real part of the dielectric modulus M' reveals low values at low frequencies and it increases as frequency increases and this is interpreted in terms of the disability of driving forces (at low frequencies) which governs the mobility of charge carriers under the influence of the electric field.
Modification of surface morphology of sputtered AZO films with the variation of the oxygen
2018, Materials Science in Semiconductor Processing
Al doped Zinc Oxide (AZO) thin films were deposited on glass substrates using DC magnetron sputtering method at different oxygen argon gas ratio. Effects of oxygen gas concentration ratio on structural, electrical and optical properties of the deposited AZO thin films were investigated by X-ray diffraction (XRD), atomic force microscope (AFM), Hall effect, ellipsometry and UV–visible spectrophotometer measurements. Results established that the films have strong c-axis orientation perpendicular to the substrate surface and exhibit better crystallinity as oxygen argon ratio increases. The lowest resistivity of 4.83 × 10⁻⁴ Ω-cm was obtained without using oxygen in the gas mixture. The average optical transmission increased from 73% to 80% in the wavelength range of 350–1100 nm and ultraviolet absorption edge shifts toward longer wavelength with the increase of oxygen argon ratio. Higher value of refractive index and a strong orange-red deep level emission was spotted in AZO thin films deposited with higher O₂/Ar ratio.
Polarization switching in undoped and La-doped TlInS<inf>2</inf> ferroelectric-semiconductors
2017, Physica B: Condensed Matter
Citation Excerpt :
Its indirect and direct band gaps are ~ 2.26 eV and ~ 2.34 eV, respectively, at 300 K [11]. It has a high photoconductivity [12] in the visible range of light. The semiconductor characteristics of TlInS2 single crystals studied by using optical and electrical measurements have been explained details in the literature.
Dielectric hysteresis loops of pure and lanthanum doped TlInS₂ ferroelectric-semiconductors were studied at the frequency 50 Hz for different temperatures below the Curie temperature ( $T_{c}$ ). It has been revealed that, without any poling procedure, pure TlInS₂ exhibits normal single hysteresis loops at $T < T_{c}$ . After electric field-cooled treatment of TlInS₂ the shape of hysteresis loops was strongly affected by corresponding charged deep level defects which were previously activated during the poling process. As a result, an additional defect polarization state from space charges accumulated on the intrinsic deep level defects has been revealed in pure TlInS₂ at the temperatures below $T_{c}$ . Besides, unusual multiple hysteresis loops were observed in La doped TlInS₂ at $T < T_{c}$ after application of different external perturbations (electric field, exposition and memory effect) to the sample. Measurements of the hysteresis loops in TlInS₂:La revealed the slim single, double and even triple polarization–electric field (P–E) hysteresis loops. This intriguing phenomenon is attributed to the domain pinning by photo- and electrically active La-impurity centers. The temperature variation of double-hysteresis loop was also investigated. Due to the heat elimination of the random local defect polar moments, the double-hysteresis loops were transformed into a normal single hysteresis loops on increasing the temperature.
Dose dependence effect of thermoluminescence process in TlInS<inf>2</inf>:Nd single crystals
2017, Optik
In this paper, thermoluminescence (TL) properties of TlInS₂:Nd single crystals were modeled using an interactive model (one trap and one kind of recombination center). The simulated work presented here was based on the experiment conducted by Delice et al. The thermoluminescence glow curve of TlInS₂:Nd single crystals has been characterized by one main peak at 26 K, which confirm the presence of one active electron trap level in the forbidden band of this material. The model used in this work is similar to other models cited previously in the literature. The calculated glow curve was in good agreement with the experimental one. Our numerical results show also that the thermoluminescence intensity increases with the increase of the dose rate (D). In the selected dose level range; the thermoluminescence response is linear and no saturation can be observed.

View all citing articles on Scopus

View full text

ReviewOptical and photoelectric properties of TlInS2 layered single crystals

Abstract

Introduction

Section snippets

Materials and sample preparation

Optical properties

Conclusion

Mater. Res. Bull.

Physica A

Thin Solid Films

Opt. Laser Technol.

Thin Solid Films

Solar Energy Mater. Solar Cells

Solid State Commun.

Thin Solid Films

J. Phys. Condens. Mat.

J. Appl. Phys.

J. Am. Chem. Soc.

Allg. Chem.

Semicond. Sci. Technol.

JETP Lett.

Review
Optical and photoelectric properties of TlInS₂ layered single crystals