Navdeep Goyal
Articles written in Pramana – Journal of Physics
Volume 40 Issue 2 February 1993 pp 97-105
Electrical and photo-electrical properties of a chalcopyrite semiconductor AgInSe_{2}
In this paper we report the electrical and photoelectrical properties of AgInSe_{2}. Nyquist plots for AgInSe_{2}, obtained at different temperatures, are perfect arcs of a semicircle with their centres lying below the abscissa at an angle
Volume 40 Issue 5 May 1993 pp 377-389
Electrical properties of nickel-doped arsenic trisulphide
Navdeep Goyal Rajni Shukla Manohar Lal
Results of temperature and frequency dependent a.c. conductivity of pure and nickel-doped a-As_{2}S_{3} are reported. The a.c. conductivity of pure As_{2}S_{3} obeys a well-known relationship: σ_{ac} ∝
Volume 42 Issue 3 March 1994 pp 187-191
Relation of coordination number to memory and threshold switching in chalcogenides
Manohar Lal Navdeep Goyal Anil Vohra
The paper reports a structural study of some memory and threshold chalcogenides in terms of coordination number
Volume 63 Issue 3 September 2004 pp 617-625
Electrical properties of a-Ge_{x}Se_{100-x}
Abdolali Zolanvari Navdeep Goyal S K Tripathi
In general, the conductivity in chalcogenide glasses at higher temperatures is dominated by band conduction (DC conduction). But, at lower temperatures, hopping conduction dominates over band conduction. A study at lower temperature can, eventually, provide useful information about the conduction mechanism and the defect states in the material. Therefore, the study of electrical properties of Ge_{x}Se_{100-x} in the lower temperature region (room temperature) is interesting. Temperature and frequency dependence of Ge_{x}Se_{100-x (x} = 15, 20 and 25) have been studied over different range of temperatures and frequencies. An agreement between experimental and theoretical results suggested that the behaviour of germanium selenium system (Ge_{x}Se_{100-x}) have been successfully explained by correlated barrier hopping (CBH) model.
Volume 76 Issue 4 April 2011 pp 629-637
Meyer–Neldel DC conduction in chalcogenide glasses
S PraKash Kulbir Kaur Navdeep Goyal S K Tripathi
Meyer–Neldel (MN) formula for DC conductivity ($\sigma_{\text{DC}}$) of chalcogenide glasses is obtained using extended pair model and random free energy barriers. The integral equations for DC hopping conductivity and external conductance are solved by iterative procedure. It is found that MN energy ($\Delta E_{\text{MN}}$) originates from temperature-induced conﬁgurational and electronic disorders. Single polaron-correlated barrier hopping model is used to calculate $\sigma_{\text{DC}}$ and the experimental data of Se, As_{2}S_{3}, As_{2}Se_{3} and As_{2}Te_{3} are explained. The variation of attempt frequency $\upsilon_0$ and $\Delta E_{\text{MN}}$ with parameter $(r/a)$, where 𝑟 is the intersite separation and 𝑎 is the radius of localized states, is also studied. It is found that $\upsilon_0$ and $\Delta E_{\text{MN}}$ decrease with increase of $(r/a)$, and $\Delta E_{\text{MN}}$ may not be present for low density of defects.
Volume 91 Issue 2 August 2018 Article ID 0025 Research Article
Meyer–Neldel energy in Se-based binary and ternary chalcogenide glasses
RAM MURTI S K TRIPATHI NAVDEEP GOYAL SATYA PRAKASH
The integral equations for DC conductivity and external conductance for the network of localised states in amorphous solids are solved by iteration method. The random free energy barriers and single polaron hoppingmodel are used to obtain the DC conductivity $\sigma_\rm{DC}$ and Meyer–Neldel energy $E_\rm{MN}$. The experimental estimates of optical band gap $E_\rm{g}$, dielectric function $\epsilon$, glass transition temperature $T_\rm{g}$ and $\sigma_\rm{DC}$ are used to calculate $E_\rm{MN}$ for Se-based binary and ternary chalcogenide glasses. The calculated values are found to be in agreement with the available experimental data. $E_\rm{MN}$ increases with increase of attempt frequency. The true pre-exponential factor $\sigma_\rm{00}$ is related to $E_\rm{MN}$ as ln $\sigma_\rm{00} = p − q E_\rm{MN}$, where $p$ is nearly 7.3 and $q$ is material-dependent. The calculated values of $E_\rm{MN}$ and $\sigma_\rm{00}$ suggest that DC conduction in these chalcogenides is due to acoustic and optical phonon-assisted polaron hopping.
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