eV For Films Research Articles

Solvent-free mechanosynthesis of Schiff bases derived from thiadiazole with potential application in sensing ionic species and NLO applications

In this work, we report the solvent-free mechanosynthesis of three Schiff bases (SBs) derived from 1,3,4-thiadiazole covalently bonded to indole (Th-In), quinoline (Th-Qn) and triphenylamine (Th-TPA) groups. This green chemistry method showed a drastic reduction in reaction time and avoidance of solvents for obtaining SBs, with good reaction yields. The molecular structures of SBs were investigated by computational chemistry calculations, with global reactivity parameters indicative of electron acceptor behavior, estimation of frontier molecular orbitals, and their theoretical band gaps of 3.49 and 3.4 eV for Th-In and Th-Qn, respectively, and the lowest of 299 eV for Th-TPA. To evaluate the possible NLO response, the hyperpolarizabilities (β) were also estimated, which are several orders of magnitude higher than the urea value used as a reference. The absorption and emission spectra were calculated using TD-DFT. These results showed a larger redshift for Th-TPA, with possible charge transfer processes more intense than those obtained for Th-In and Th-Qn. The photophysical properties of the Schiff bases were determined, with band gap values for Th-In, Th-Qn, and Th-TPA of 2.53, 2.66, and 2.39 eV in solution and 2.77, 2.26, and 2.21 eV in film, respectively. When the SBs were evaluated as potential naked-eye colorimetric chemosensors, colorimetric changes were observed in Fe2+, Fe3+, Pb2+, Cu2+, and Ag+ ions, with Ag+ being the most promising. Z-scan was used to evaluate the nonlinear response of the SBs and showed saturable absorber behavior with self-focusing processes. Cyclic voltammetry was used to determine the electrochemical band gaps, which were 2.70, 2.71, and 1.98 eV for Th-In, Th-Qn, and Th-TPA, respectively. Th-TPA exhibits superior optical and electrical properties among the three SBs investigated. In addition, it exhibits photochromism, which can be used in conjunction with its other properties in NLO and sensor applications.

Colorless Near-Infrared Absorbing Dyes Based on B-N Fused Donor-Acceptor-Donor π-Conjugated Molecules for Organic Phototransistors.

The introduction of a colorless function to organic electronic devices allows responses to light in the near-infrared (NIR) region and is expected to broaden the applications of these devices. However, the development of a colorless NIR dye remains a challenge due to the lack of a rational molecular design for controlling electronic transitions. In this study, to suppress the π-π* transitions in the visible region, polycyclic donor-acceptor-donor π-conjugated molecules with boron bridges (Py-FNTz-B and IP-FNTz-B) are designed and synthesized, which contain pyrrole or indenopyrrole as donor units with fluorinated naphthobisthiadiazole (FNTz) as an acceptor unit. The pyrrole end-capped Py-FNTz-B shows an absorption band in the NIR region without distinct visible-light absorption, which has led to the establishment of colorless characteristics. The indenopyrrole end-capped IP-FNTz-B shows a narrow optical energy gap of 0.87eV in films. Time-resolved microwave conductance and field-effect transistors demonstrate the semiconducting characteristics of these molecules, and Py-FNTz-B-based devices function as NIR phototransistors. Theoretical analyses indicate that the combination of a polyene-like electronic structure with orbital symmetry is important to obtain NIR wavelength-selective absorption. This study suggests that a molecular design based on electronic structures can be effective in the development of colorless NIR-absorbing dyes for organic electronics.

Stable Electron Spin Pan on Aromatic Oxalic Acid Radical

Comprehensive SummaryThe stability of organic radicals in ambient condition is important for their practical application. During the development of organic radical chemistry, the electron‐withdrawing and steric hindrance groups are usually introduced to improve the stability of radicals via reducing the reactivity of radicals with oxygen in air. Herein, the electron‐withdrawing carbonyl groups are introduced to construct a planar aromatic oxalic acid radical (IDF‐O8) with two‐dimensional electron spin pan structure. Interestingly, IDF‐O8 exhibited a low optical bandgap of 0.91 eV in film, however, the multiple quinone resonance structures between electron‐withdrawing ketone and phenol radicals contribute to the high stability of open‐shell radical IDF‐O8 without protection of large steric hindrance groups. Under the irradiation of 808 nm (1.2 W·cm–2), IDF‐O8 reaches 147 °C in powder state. This work provides an efficient synthesis route for the open‐shell electron spin pan system, which is different from the famous fullerene, carbon nanotube and graphene. The electron spin pan can be extended to spin tube or spin sphere system based on the design strategy of aromatic inorganic acid radicals in future.

Microstructural and physical properties of samarium orthoferrite thin films by the sol–gel method

Samarium orthoferrite, SmFeO3 (SFO), is a multifunctional material with promised applications. In this paper, SFO thin films were prepared by sol–gel method onto a quartz substrate at different annealing temperatures (T = 700, 750, 800 and 850 °C) and onto LaNiO3 (LNO) buffered quartz substrate using T = 800 °C. The phase formation, microstructure, electronic, optical, magnetic and ferroelectric properties of the films were investigated and compared. Minimal annealing temperature (T) from thermogravimetric analysis was about 720 °C. From X-ray diffraction analysis, film T = 700 °C showed mixed phases of SFO and a trace amount of Sm2O3 while single phase of SFO was observed for films T = 750 – 850 °C. The lattice parameter c and microstrain reduced for films T = 700 – 800 °C and then increased for film T = 850 °C. From Atomic force microscopy analysis, the porosity, root mean square roughness and particle size of the films increased with the rise of T. All films exhibited high optical transmittance (∼79 – 95 %) in 800 – 550 nm wavelength range and showed two main optical absorptions peaks at about 285 and 385 nm. At lower energy transition, the band gap (Eg) reduced from ∼ 2.79 to 2.72 eV for films T = 700 – 800 °C and then increased to ∼ 2.79 eV for film T = 850 °C. The film’s magnetisation (Ms) tended to increase with T increment. The SFO/LNO film showed higher Ms and Eg than film T = 800 °C.

Influence of Bi addition on the optical properties of As40Se60 thin films

In the present work, structural, microstructural, compositional and electronic band gap properties of As40Se60 and As40Bi15Se45 bulk and thin films are reported. The films were prepared by thermal evaporation technique under high vacuum. X-ray diffraction (XRD) study indicated amorphous nature of As40Se60 in bulk prepared by melt quenching technique. Bi incorporation in As40Se60 with composition Bi15As40Se45 however led to nucleation of Bi2Se3 nanocrystallites in the amorphous matrix of As40Se60. The films made out of the two targets of composition As40Se60 and As40Bi15Se45 did not show any XRD peak, indicating their amorphous nature. UV-Visible-NIR spectroscopic study indicated a large decrease in the electronic band gap from 1.74 eV in films of composition As40Se60 to 1.28 eV for compositon Bi15As40Se45. This decrease is explained on the basis of a high concentration of defect states leading to the presence of localized states in the band gap due to Bi incorporation. Field emission scanning electron microscopy (FESEM) images show smooth and homogeneous surface for the As40Se60 films, while Bi incorporation led to increases of the surface roughness in the Bi15As40Se45 films. The decreased band gap and increased surface roughness on Bi incorporation in As40Se60 films indicate the suitability of these films for solar cell applications.

The effect of three-minute exposure of oxygen plasma on the properties of tin oxide films

Research devoted to the effect of three-minute exposure of oxygen plasma on the properties of tin oxide films investigation. The films were obtained by sol-gel method from five-water tin tetrachloride solution. The concentration of tin ions in the SnCl4/EtOH film-forming system was 0.14 mol/l. The solution system was deposed on the glass substrate by carring out a modified dipping method. Plasma treatment was performed at a pressure of 6.5 Pa and a power of about 20 Watts. The frequency of the oscillations produced by the generator was 27.12 ± 0.6 % MHz as well. The temperature of the samples during processing did not exceed 100 ºC. As a result of the formation of tin oxide (II), the film transmittance decreased after treatment with oxygen plasma. The width of the electric forbidden zone of the obtained samples was calculated, which was 3.95 eV for glass and 3.79 eV for film. The resistance of the films was determined by 10 measurements on different parts of the samples. The film without processing has a resistance of about 4255 ± 1158 kΩ, after processing, the resistance decreased by 25 times and amounted to 167 ± 26 kΩ. A decrease in resistance indicates an increase in the concentration of charge carriers in the sample. The resulting SnO is a semiconductor that lowers the transmittance of the studied films and contributes to reducing their resistance. X-ray structural analysis of the samples was also performed. After processing in oxygen plasma, the intensity of reflection from the (110) plane have increased. It should be noted that the number of planes with (101) indexes has decreased. The study of the sample surface showed the destructive nature of three-minute exposure by oxygen plasma.

Fabrication of Li1+xAlxGe2-x(PO4)3 thin films by sputtering for solid electrolytes

Li1+xAlxGe2-x(PO4)3 (LAGP) thin films have been grown on sapphire substrates by RF magnetron sputtering and post annealing. The effects of varying sputtering parameters such as power and pressure were studied, and the deposited films were characterized to investigate how the ionic conductivity values depend on the microstructure. The composition of as-sputtered films was found to be more strongly influenced by power than the pressure. The films deposited at lower powers, which results in lower deposition rates, have compositions similar to that of the target. Heating the substrates during deposition is found to minimise the formation of pinhole defects in films subsequently annealed at higher temperatures. Post annealing leads to a gradual transformation from the as-sputtered amorphous phase to crystalline LAGP thin films. At high annealing temperatures (above 700 °C) both porosity and the GeO2 impurity phase appear in the films and result in lower ionic conductivities. We have optimised the processing conditions to achieve ionic conductivities in excess of 10−4 Scm−1 and activation energies as low as 0.31 eV in films only 1 μm thick, suggesting that LAGP could offer attractive properties as a thin film battery electrolyte material.

Effects of precursor concentration on the microstructural, optical and photoelectrochemical properties of Bi2O3 films synthesized by sol-gel method

β-Bi2O3 films were prepared by sol-gel method process from solutions with different precursor concentration (M = 0.05–0.20). The films were characterized by X-rays diffractions (XRD), field emission electron microscopy (FESEM), atomic force microscopy (AFM), UV–vis spectroscopy, photoluminescence spectroscopy (PL), photoelectrochemical (PEC) and electrochemical impedance measurements. The Bi2O3 deposited film had single phase β-Bi2O3 on ITO substrate while it exhibited mixed phases of ε-, δ- and β-Bi2O3 on glass substrate. By increasing M above 0.05, more XRD patterns were observed and lattice parameter c increased. Besides, crystallite size of films increased first from 19.2 to 26.4 nm at M = 0.05 – 0.15 and then decreased to 19.4 nm at M = 0.20. From AFM, the films consisted of polyhedron-like shape islands with height and distribution increased with increment of M. The surface roughness increased from 10.3 to 18.5 nm for film with M = 0.05 and 0.15, respectively, and then decreased to 14.8 nm for film M = 0.20. Optical band gap decreased from 3.24 eV for film M = 0.05 to 2.89 eV for film M = 0.20. From PEC, photocurrent of films increased with increment of M and had maximum value 3.8 × 10−4 A/cm2 for film M = 0.20 at 0 V versus Ag/AgCl. Electrochemical impedance analysis showed a gradual reduction of charge transfer resistance with increasing M. Finally, β-Bi2O3 films with tailored microstructure were prepared which make it attractive for many applications.

Optical Transmission and Reflection of Nanostructured Cu(In,Ga)Se2 Thin Films Irradiated with Hydrogen Ions

The bandgaps of 1.187[Formula: see text]eV in non-irradiated nanostructured thin films of Cu(In,Ga)Se2 (CIGSe) and of 1.182[Formula: see text]eV in those films irradiated with 10[Formula: see text]keV hydrogen ions were determined using optical transmission and reflection spectroscopy at 4.2[Formula: see text]K. The observed reduction in the bandgap is assigned to the formation of secondary antisite defect complexes inducing band tails of the density of states in the valence band.

Mechanosynthesis of Photochromic Oligophenyleneimines: Optical, Electrochemical and Theoretical Studies.

In this work, two oligophenyleneimines type pentamers with terminal aldehydes, designated as DAFCHO (4,4′-((((((2,5-bis(octyloxy)-1,4-phenylene)bis(methanylylidene))bis(azanyl ylidene))bis(9H-fluorene-7,2-diyl))bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy) benzaldehyde)) and FDACHO (4,4′-((((((2,5-bis(octyloxy)-1,4-phenylene)bis(methanylylidene))bis (azanylylidene))bis(4,1-phenylene))bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy) benzaldehyde)) were synthesized by mechanochemistry method using 2,5-bis(octyloxy) terephtal aldehyde and 2,7-diaminofluorene or 1,4-phenylenediamine. All compounds were spectroscopically characterized using 1H and 13C-NMR, FT-IR and mass spectrometry MALDITOF. The optical properties of the compounds were analyzed by UV-vis spectroscopy using different solvents. We observed that DAFCHO and FDACHO exhibit interesting photochromic properties when they are dissolved in chloroform and exposed to sunlight for 3, 5 and 10 min. The value of the energy band gap was calculated from the absorption spectra without irradiation Egap(optical). It was 2.50 eV for DAFCHO in chloroform solution, and it decreased to 2.34 eV when it is in films. For FDACHO, it was 2.41 eV in solution and 2.27 eV in film. HOMO (Highest Occupied Molecular Orbital), LUMO (Lowest Unoccupied Molecular Orbital) and Egap(electrochemical) values were obtained by electrochemical studies. The results indicate that the compounds can be considered as organic semiconductors since their values are 2.35 eV for DAFCHO and 2.06 eV for FDACHO. The structural and electronic properties of the compounds were corroborated with a DFT (Density Functional Theory) study.

Studies on structural, optical, electrical and morphological properties of LiCoO2 thin films prepared by sol–gel method

In the present investigation, lithium cobalt oxide (LiCoO2) thin films were synthesised by the sol–gel process coupled with a cost-effective spin coating method using citric acid as a chelating agent. The films prepared on mineral glass substrates were annealed at different temperatures of 548–748 K in steps of 50 K. The XRD studies revealed that the LiCoO2 thin films annealed at a lower temperature exhibit semi-crystalline nature and transform to crystalline structure with an increase in the annealing temperature. The optical band gap energy of the films was found to vary from 2.51 to 3.24 eV for films annealed at temperatures in the range of 548–748 K. The electrical conductivity of the LiCoO2 thin films varied from 10−3 to 10−9 Ω−1 cm−1 due to variation in the annealing temperature.

Magnetocrystalline anisotropy of ε-Fe2O3

The epsilon Fe2O3 phase of iron oxide has been studied to understand the spin structure and the magnetocrystalline anisotropy in the bulk and in thin films of ε-Fe2O3 and Co-doped ε-Fe2O3. The preferential magnetization direction in the nanoparticles of ε-Fe2O3 is along the a-axis [M. Gich et al., Chem. Mater. 18, 3889 (2006)]. Compared to the bulk band gap of 1.9 eV, the thin-film band gap is reduced to 1.3 eV in the Co-free films and to 0.7 eV in the film with partial Co substitution. The easy magnetization direction of the bulk and Co-free ε-Fe2O3 is along the c-axis, but it switches to the a-axis on Co substitution. All three systems exhibit in-plane anisotropies associated with the orthorhombic crystal structure of the oxide.

The formation of α-phase SnS nanostructure from a hybrid, multi-layered S/Sn/S/Sn/S thin films: Phase stability, surface morphology and optical studies

Single phase of SnS thin film was fabricated from S/Sn/S/Sn/S multilayer prepared by using atmospheric pressure and vacuum thermal evaporation methods Glancing angle high vacuum thermal evaporation technique was employed to grow Sn nanorods which facilitated the sulphur diffusion in a faster manner to prepare SnS nanoparticles. The sulphur deposition temperature, sulphur deposition time and tin deposition time were successfully tailored in the synthesis process and stabilized α-phase SnS by probing through confocal micro-Raman spectrometer. X-ray diffraction confirms the formation of SnS crystal structure at sulphur deposition temperature 200°C. The mechanism of formation of highly porous SnS phase with flower like morphology is explained from the morphological analysis of post deposition annealed film. The complete absence of any oxidation state as evident from Raman as well as EDAX analysis confirms that the proposed sulphurization method could be a suitable, simple and cheap technique for the successful sulphurization of metal films. Band gap calculation from Tauc plot showed a direct band gap value of 1.5eV for films with single phase of SnS which can be used as a p-type absorber layer in thin film solar cells. Emission studies showed the energy transitions attributed to band edge transition and due to the presence of intrinsic defects.

4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophen‐4‐one (CPDTO) homopolymer with side chains on every other CPDTO

ABSTRACTA soluble 4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene‐4‐one (CPDTO)‐based polymer (C6‐PCPDTO) has been synthesized from two monomers derived from nonalkylated CPDTO and didodecyl CPDTO (C12‐CPDTO). Proton NMR, thermal analysis, UV–vis absorption, cyclic voltammetry, and XRD are used to characterize the polymer in solution and film. The new polymer has an optical bandgap of 1.28 eV in film, and has strong interchain interaction in chloroform solutions. The polymer contains a significant amount of homocoupled segments. The regular segments and homocoupled CPDTO segments render the polymer highly aggregating in solution. The non‐planar homocoupled C12‐CPDTO segments prevent the polymer from forming regular π‐stacks, resulting in a low SCLC hole mobility (3.88 × 10−7 cm2V−1s−1). CV experiments show that C6‐PCPDTO is stable in its oxidized and reduced states. Solar cell devices were fabricated from C6‐PCPDTO2:PC60BM blends of different weight ratios. High PC60BM loading (80% or greater) was required for the devices to show measurable efficiency, indicating that the limited π‐stacking of the polymer is not sufficient to cause effective phase separation. Further development of synthetic method is still needed to eliminate structural defects so that long‐range ordered pi‐stacking can be realized in the polymer for these applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1077–1085

P-Type highly conductive and transparent NdF3-doped tin oxide films prepared by dip coating

Transparent p-type conducting oxide (TCO) films with high conductivity and transparency are in great need to couple with n-type TCO for various electro-optical devices. The purpose of the current study is to explore p-type TCO films with low electrical resistivity and high optical transmittance. We prepared NdF3-added SnO2 (NFTO) thin films, with 0 to 5mol% NdF3, on a glass substrate by sol–gel dip-coating and post-annealed at 475°C. Structural, optical and electrical properties of the resultant NFTO films were investigated. X-ray diffraction patterns indicate tetragonal rutile SnO2 structure with a preferred (110) orientation for all studied films. The absence of impurity peaks indicates that Nd and F atoms may completely dissolve in SnO2 lattice. All films showed excellent transmittance of 84.7 to 90.6% at a wavelength of 550nm. Optical band gap of the NFTO films reduces from 3.94eV for un-doped film to a minimum of 3.75eV for the film with 4mol% NdF3. We confirmed p-type conduction of NFTO films using both Hall-effect and Seebeck coefficient measurements. The film with 2mol% NdF3 shows the lowest electrical resistivity, 8.2×10−3Ωcm, the highest hole-concentration, 8.96×1019cm−3 and a Hall mobility of 9.74cm2V−1s−1. The developed p-type NdF3 added SnO2 TCO films can couple with n-type SnO2 TCO for homo-junctions, which will lead to wide applications in optoelectronics.

6-(2-Thienyl)-4H-thieno[3,2-b]indole based conjugated polymers with low bandgaps for organic solar cells

Two copolymers of donor–acceptor (D–A) type based on 6-(2-thienyl)-4H-thieno[3,2-b]indole (TTI), electron-pushing unit, were synthesized and explored in organic solar cells. 4H-thieno[3,2-b]indole (TI), which has indole fused with thiophene, was coupled with another thiophene to form TTI which was connected with electron-pulling units 2,1,3-benzothiadiazole (BT) and 2,2-dimethyl-2H-benzimidazole (MBI) for efficient ICT effect to generate low bandgaps. PTTIBT, with TTI and BT units, and PTTIMBI, with TTI and MBI units, are expected to provide broader absorption spectra and smaller bandgaps than polymers based on carbazole. PTTIBT and PTTIMBI, with good solubility in organic solvents, show optical bandgaps of 1.69 and 1.57eV in films, respectively. The PTTIMBI shows higher PCE value as compared to that of PTTIBT with the device fabricated using a PTTIMBI:PC71BM(1:1.5w/w) blend.

Annealing Temperature Effect on Properties of Chemically Deposited PbTe Films and Bulk

Abstract The PbTe films were deposited onto glass substrate (microscopic slices) by a chemical bath method (CBD) at room temperature. The deposited films are dense, smooth, and uniform with silver gray metallic luster structure. Using XRD, it found that the structure of PbTe possesses stable face centered cubic (fcc) phase. The grain size of the PbTe bulk increased within the range of 33– 57 nm with annealing temperature increasing. AFM micrographs of surface of the prepared film are observed that horizontal distance in the rang (230– 395) nm. The band gaps of the PbTe are determined from UV-Vis spectrophotometer and are found to be within the range ( 0.39 - 0.95) eV. Energy band gab of PbTe which determined from FT -IR spectrophotometer is (0.36ev). The activation energy varied from 0.35- 1.72 eV for films and from 0.11-0.34 eV for bulk with annealing temperature variations from 373-573K. Films and bulk exhibit p-type conduction and resistivity in the range (75×10-4 Ω. cm - 146×10-4 Ω.cm). The carriers density and Hall mobility in PbTe bulk were in the rang 5.8 ×1023 m-3 and 4.004 m2/Vs.

Optical investigation of oxygen diffusion in thin films of Gd-doped ceria

We describe the use of null-ellipsometry with lock-in detection to monitor grain core oxygen diffusion in thin films of the solid-state ionic conductor Ce0.8Gd0.2O1.9. Application of an electric field perpendicular to the film surface—probe alternating voltage (UA) in addition to perturbation bias voltage (UB)—produces ellipsometer optical response at the probe frequency. The signal amplitude and time dependence can be interpreted in terms of changes in the local material polarizability. Since the ionic contribution to the material polarizability is much larger than that of electrons or protons, the diffusion of ions can be distinguished. Because grain cores occupy the majority of the film volume, ion diffusion in the grain cores dominates the optical response. This effect was studied as a function of temperature (75–160°C), amplitude and frequency of the electric field. The activation energy for oxygen diffusion in the grain cores was found to be 1.1±0.1eV and 1.5±0.1eV for films with in-plane compressive strain of 0.34±0.06% and in-plane tensile strain 0.16±0.03%, respectively.

Electrical conductivity of Gd-doped ceria film fabricated by aerosol deposition method

Gd-doped ceria (GDC) films were deposited on various substrates using aerosol deposition (AD) method in order to determine whether this process is useful for the fabrication of thin (~1μm) electrolyte layers. The AD method is attractive because no vacuum equipment or target material is required. Although the AD method utilizes pre-calcined powder for the deposition of film, the particle size and microstructure of films are largely dependent upon the choice of substrate (sapphire, glass, Si–Pt). The film deposited on sapphire substrate had a relatively dense microstructure and the smallest particle size. Total conductivity of film was measured using either in-plane or across-plane mode depending upon the substrate. Across-plane measurement gave a lower conductivity than in-plane measurement, possibly due to the difficulty of current collection or anisotropic microstructure. The magnitude of in-plane conductivity was comparable to the conductivity of a bulk sample, i.e., ~1.2×10−3S/cm at 450°C for the film deposited on sapphire. The activation energy of electronic conductivity at 300–450°C was also similar, ~2.23eV. However, the activation energy of ionic conductivity differed depending upon the substrates: ~0.71eV for the film on sapphire substrate and 0.93–0.94eV for other films. The Po2 dependence had a −1/4 slope, similar to that of bulk or film form of GDC at higher (>500°C) temperature. Overall, the AD method may be useful for the deposition of thin-film GDC since the conductivity was similar with that of film or bulk samples fabricated by conventional methods.

Effects of Si-ion implantation on crystallization behavior of Ge2Sb2Te5 film

Crystallization and thermal stability of Ge2Sb2Te5 (GST), the benchmark working material in phase-change non-volatile memory, were modified via Si-ion implantation. Through 5×1015 Si-ions/cm2 ion-implantation, crystallization temperature increases from 165°C to 177°C. Furthermore, the activation energy of crystallization increases from 2.9eV in the pristine film to 3.3eV and 4.0eV in films implanted with the doses of 5×1015 and 5×1016 Si-ions/cm2, respectively. Temperatures corresponding to a 10-year failure-time increase from 83°C in the pristine film to 96°C and 107°C in films implanted with 5×1015 and 5×1016 Si-ions/cm2, respectively. Thermal stability of Si-ion implanted GST thus improves significantly. It was also found that grain growth is inhibited with higher implantation doses. In the case of the 5×1016 ion/cm2 dose, the second-phase transition from face-centered cubic to hexagonal closed-packed structure of the GST is completely inhibited. However, crystallization time increases slightly due to Si-ion implantation.