To study the optical and structural properties of Si15Te85−xCux (1 ≤ x ≤ 10) thin film series, the bulk materials are formulated by melt quenching technique at a base pressure of 10−6 mbar. Bulk materials (powder) of various compositions are deposited on glass substrate by flash evaporation method. The optical properties of Si15Te85−xCux (1 ≤ x ≤ 10) thin film series are investigated by means of absorption, transmission and reflection measurements in the spectral region between 300 and 780 nm. The variation of the optical band gap from 0.75 to 1.13 eV is supported by the average bond energy of the system and reveals an intermediate phase in the range 3 ≤ x ≤ 6. The refractive index is in the range of 0.4 to 3. The variation of Urbach’s energy with an increase in the intensity of copper doping is in the range of 6.28 to 24.62 meV. XRD results confirm the amorphous character of the deposited thin films. EDXS carried out on Si15Te85−xCux (1 ≤ x ≤ 10) thin film series confirms the composition. SEM images show continuous granular deposition proving the amorphous nature and elemental mapping confirms the presence of all elements in the deposited thin films. AFM is used for roughness study. These results emphasize the applicability of the series for several potential optical applications like laser diodes, amplifiers, photo detectors etc.

I-V characterization of the bulk and amorphous thin film of the as-prepared Si 15 Te 80 Cu 5 sample is carried out to better perceive the electrical switching behavior. Memory and threshold switching have been discerned in bulk glass, but only memory switching has been shown by amorphous thin films. The thin film device exhibits a substantially lower threshold voltage than its bulk version, suggesting that it could be used for phase change memory (PCM). The glass is subjected to Set –Reset using a triangle pulse of 6 mA for set operation and a rectangle pulse of 12 mA for reset operation to determine the suitability of the provided glass for PCM use. A constant recurrence of a few Set-Resets is evident in this study. Morphological study has also been carried out on the bulk sample.

Thermal properties have been investigated using alternating differential scanning calorimetry (ADSC) for determining the phase transitions of Si(20)Te(80-x)Snx glass samples (1 <= x <= 6). Experiments are performed to assess the variations of thermal characteristics such as glass transition temperature (T-g) and crystallization temperature (T-c) etc. as a function of Sn variation. The glass-forming ability (GFA) and thermal stability (AT) are analyzed for understanding the suitability of as-prepared material in terms of network connectivity and rigidity. The studies have revealed minimum non-reversing enthalpy (Delta H-NR) value between compositions (2 <= x <= 5) of Si20Te80-xSnx glasses, which serve as a basis of the existence of Boolchand's intermediate phase (BIP). It is observed that an increase in Sn dopant resulted in an increase in the density and decrease in the molecular volume of Si 20Te80-xSnx samples. These studies reveal the correlation with the memory switching behavior displayed by Si20Te80-xSnx glasses.

To understand the electrical switching behavior of Si 15 Te 85-x Cu x (1≤ x ≤10) series, I-V characterization has been performed on bulk as well as amorphous thin films of the as-prepared samples. Both the bulk glasses and amorphous thin films are found to manifest memory-type switching behavior. The threshold voltages of thin-film devices are found to be much lower than the bulk counterparts and hence could find application for phase change memory (PCM). The composition analyses of both have divulged the existence of intermediate phase (IP) in the composition range of 2 ≤ x ≤ 6. To examine the probability of the given glass for PCM application, Set-Reset studies have been performed on the glasses with a triangular pulse of 6 mA for set operation and rectangular pulse of 12 mA for the reset operation. The study has revealed a continuous repetition of few Set-Reset cycle by the Si-Te-Cu series. Raman studies carried out on the bulk glasses report the occurrence of blue shift over the composition in a regular manner. Further, SEM studies have been carried out on Si-Te-Cu samples to understand the morphological changes that would have occurred during switching. Additionally, thickness dependence of threshold voltage of representative Si 15 Te 80 Cu 5 and Si 15 Te 76 Cu 9 glasses has been carried out to reveal the relationship between threshold voltage and thickness.

Alternating differential scanning calorimetry (ADSC) analysis has been carried out on bulk Si15Te85-xCux (1 <= x <= 10) glasses to examine the thermal properties of the glassy samples in detail. The investigations on the compositional dependence of Delta H-NR (non- reversing enthalpy) manifests a trough between the composition 2 <= x <= 6 which stands as the basis of the presence of Boolchand's Intermediate phase in that range. Additionally, anomalous behavior has been observed at the compositional dependence of various thermal parameters at x = 9, which stipulates the appearance of chemical threshold at the stated composition. Annealed bulk samples have been exposed to XRD studies to discern the type of formed crystalline phases. The study has reported the manifestation of Te, Si1Te2, Si2Te3, Cu3Te2 phases.

The Si20Te80-xSnx (1 <= x <= 7) glasses are synthesized using melt quenching technique. Result of X-ray diffraction (XRD) exhibits the non-crystallinity of the prepared samples. Depending on applied on state current, the synthesized Si20Te80-xSnx (1 <= x <= 7) samples show both threshold and memory type of behavior. The composition dependence of threshold voltage (V-th) displays a decrease in the Vth values. Further the composition and morphological studies are carried out using Energy Dispersive X-ray analysis (EDAX) and Electron microscopy (SEM). The differential scanning calorimetry (DSC) is used for crystalline peak studies. Using DSC, the crystallization temperature (Tc) of representative glass samples are found. The crystalline peak studies are carried out by annealing representative samples at their respective Tc for two hours to find different phases present in the samples. The SET-RESET studies are performed to find the applicability of the given material in phase change memory (PCM) applications.

This paper describes the various studies performed on a representative quaternary thin film device of composition Ge15Te70In5Ag10, which could be an important material for phase change memory and data storage application. The I-V Characteristics (Switching characteristics), X-RAY Diffraction (XRD) and Energy-Dispersive X-ray analysis (EDAX) studies have been performed to show that the given material has some favorable characteristics as its application as phase change memory (PCM).

Amorphous Ge15Te80–xIn5Agx ( $6\le {x} \le24$ ) thin films prepared in sandwich geometry exhibit memory switching behavior unlike the bulk sample that has shown both threshold switching for less current (1–2 mA) and memory switching for current greater than 2 mA. As anticipated, the threshold voltage of Ge15Te80–xIn5Agx( $6\le {x} \le24$ ) thin films is found to be lower as contrast to those of bulk counterparts. The compositional dependence of amorphous system shows an extensive plateau in the range of $\textsf {6} \le {x} \le \textsf {12}$ which literally stands for the intermediate phase after which there is a drastic increase in the threshold field. Shifted rigidity percolation threshold has also been confirmed from the compositional dependence of threshold field of amorphous Ge15Te80–xIn5Agx thin films. In addition, the optical bandgap of a-Ge15Te80–xIn5Agx thin-film sample has been reckoned considering absorption spectra, and the compositional dependence has been described based on average bond energy of the system.

Bulk Si20Te79Sn1 glass is prepared by melt-quenching method, amorphous nature of the as-quenched glass is confirmed by XRD. I-V characteristics reveals that Si20Te79Sn1 bulk sample exhibits threshold type electrical switching behavior. The thermal parameters such as crystallization temperature, glass transition temperature are obtained using differential scanning calorimetry. The crystalline peak study of the sample annealed at crystallization temperature for 2 hr shows that the Sn atom interact with Si or Te but do not interact with the Si-Te matrix in a greater extent and it forms a separate phase network individually.

The electrical switching studies of Si based ternary material with composition Si15Te84Cu1 has been presented in this paper. The material has been prepared in both bulk and thin film device form. The bulk sample is prepared by melt quenching technique. The thin film device is prepared in sandwich geometry on a glass substrate with copper as top and bottom electrodes. The material Si15Te84Cu1 is coated by flash evaporation technique and the electrodes by sputtering technique in DC mode. To carry out SET studies, electric field is employed to the device and it has been found that the thin film device exhibits memory type of switching. The essential instruments used in the fabrication of amorphous switching devices are high temperature furnace and deposition units like flash evaporation unit, sputtering unit. Keithley source-measure unit along with two probe station succoured the study of electrical switching behaviour of the device. A morphological study has been carried out with Scanning Electron Microscopy and it has revealed some structural changes, which have occurred during switching.

Bulk ingots of Si15Te85-xCux (1 <= x <= 5) glasses are concocted by typical melt quenching technique. XRD validate the non-crystalline feature of the prepared quenched sample. The samples are found to display threshold type of electrical switching behavior. The switching behavior on all the samples is noticed without any disturbances. Compositional dependence of threshold voltage of Si15Te85-xCux (1 <= x <= 5) glasses has been studied and it has been found that VT increases as the atomic percentage of dopant (copper) increases in the host matrix. The distinguished behavior has been envisaged and correlated to the improvement in network connectivity and rigidity with the addition of Cu.