Effects Of Post-thermal Annealing Research Articles

Effects of hydrogen doping on the phase structure and optoelectronic properties of p-type transparent SnO

Hydrogen (H) is a ubiquitous impurity, which can significantly affect the phase structure and the optoelectronic properties of oxide semiconductors. To date, a well-established understanding of the effects of H doping on the properties of p-type transparent SnO is still lacking. Here, we present a comparative study to reveal the role of H in SnO films by magnetron sputtering. We find that in as-grown undoped SnO films, in addition to the tetragonal SnO phase, secondary phases of SnO2 or Sn3O4 are present under certain growth temperatures. In contrast, a small fraction of metallic Sn phase is included in the as-grown H-doped SnO (SnO:H) films, attributed to the partial reduction of SnO by the H2 in the sputtering gas. Effects of post thermal annealing (PTA) on the properties of SnO films are also explored. Results strongly indicate that H doping or PTA facilitates the formation of Sn phase and Sn vacancies related defects, giving rise to the p-type conductivity observed in the undoped or H-doped SnO films. The present study provides a comprehensive understanding of the evolution of phase structures as well as defect properties of SnO films, which is crucial for their future studies and optoelectronic applications.

Effect of Post-thermal Annealing on the Structural, Morphological, and Optical Properties of RF-sputtered In2S3 Thin Films

Indium sulfide films were deposited by radio frequency magnetron sputtering technique on soda lime glass substrate. The deposition was conducted at the temperature of 150 °C and prepared films were then thermally annealed under argon atmosphere at 350 °C and 450 °C for 30 min. The impact of post-thermal annealing treatment on the properties of the films was investigated. From X-ray diffraction analysis, the formation of the stable tetragonal β-In2S3 crystal structure was substantiated and revealed that the thermal annealing treatment at 450 °C improved the crystallization of the films. The change in surface topographies and morphologies of the films depending on the post-thermal annealing process were examined by atomic force microscopy and scanning electron microscopy techniques, respectively. The stoichiometric ratio of constituent elements in the films was obtained by elemental analysis and it was seen that the films had slightly sulfur (S) deficit composition. It was found that the concentration of S slightly increased with the thermal annealing process. The room temperature photoluminescence spectra revealed that the films included vacancies of sulfur (VS: donor) and indium (In) (VIn: acceptor), indium interstitial (Ini: donor) and oxygen (O) in vacancy of sulfur (OVs: acceptor) defects with strong and broad emission bands at around 1.70, 2.20, and 2.71 eV.

Tin instead of aluminum as a back electrode in P3HT:PC71BM organic solar cells

In the present work, a thin film of Sn metal, instead of aluminum, was deposited as a back electrode, using thermal evaporation, for fabricating organic solar cells composed of poly(3-hexylthiophene) and [6,6]-phenyl-C71 butyric acid methyl ester. The effect of post-thermal annealing on performance parameters of the solar cell was investigated at low temperatures (suitable for organic solar cells) up to 180 °C. In addition, the effect of thermal annealing on morphological (using scanning electron microscopy) and electrical properties (using a Hall effect setup) of the Sn thin films is reported and discussed here. The obtained minor effect of thermal annealing on the morphological and electrical properties of the Sn thin films is offset by an improvement in the performance parameters of the solar cells after post-annealing at 160 °C. The present study shows good electrical properties of Sn thin films which are comparable with those of aluminum thin films.

150 KeV proton irradiation effects on photoluminescence of GaInAsN bulk and quantum well structures

Low-temperature (T = 30 K) photoluminescence (PL) and post thermal annealing effects on 150 KeV proton irradiated GaInAsN bulk, single quantum well and triple quantum well structures (Eg ~1.0 eV) have been investigated. The nitrogen proportion of the samples was confirmed by high-resolution X-ray diffraction (HR-XRD) measurement as 0.26%, 0.30% and 0.20% for GaInAsN bulk, SQW, and MQW samples, respectively. The result shows that the PL intensity of GaInAsN materials degraded seriously by proton irradiation. The PL intensity enhancement were observed for all three types of sample after thermal annealing at 650 °C for 5 min, and MQW sample was recovered by the factor bigger than 100. The irradiation induced red-shift and thermal annealing induced blue-shift phenomena were analyzed by SRIM simulation result and theoretical models of InGaAs band structure.

Effect of Post-Thermal Annealing on the Performance and Charge Photogeneration Dynamics of PffBT4T-2OD/PC71BM Solar Cells.

In this work, we studied influence of post thermal annealing on the performance and charge photogeneration processes of PffBT4T-2OD/PC71BM solar cells. As-prepared device exhibits a high-power conversion efficiency of 9.5%, much higher than that after thermal annealing. To understand this phenomenon, we studied charge photogeneration processes in these solar cells by means of time resolved spectroscopy. We associate the degradation of solar cell performance with the reduction of exciton dissociation efficiency and with increased bimolecular recombination of photogenerated charges as a result of annealing. We correlate the generation of localized PffBT4T-2OD polarons observed via spectro-electrochemical measurements with enhancement of the bimolecular charge recombination of annealed solar cells.

The effect of thermal annealing on the layered structure of smectic liquid crystalline organic semiconductor on polyimide gate insulator and its OFET performance

The electrical performance of organic field-effect transistors (OFETs) depends on the quality of thin-film organic semiconductors, which is significantly affected by solution-processing conditions and additional processes. We investigated the effects of post-thermal annealing on the thin-film morphologies of liquid crystalline organic semiconductors on polyimide gate insulator surface and the FET performances of the films. The active material selected for the OFETs was 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-C10), which shows a highly ordered smectic E (SmE) mesophase and polycrystalline thin films feature very high mobility. We aimed to produce well defined molecular orientation and crystal structure in thin-film Ph-BTBT-C10 on polyimide gate insulator not typical SiO2 gate insulator via thermal annealing process. Uniform bilayer- or monolayer-structured polycrystalline thin films were obtained on polymer gate insulator after thermal annealing at a SmE (over 148°C) and SmA (over 213°C) liquid crystalline phase temperature, respectively. The OFET using bilayer-structured thin film showed high performance with a mobility of 2.27cm2/Vs.

Thermal annealing impact on crystal quality of (GaIn)2O3 alloys

In this study, we investigated the phase separation phenomenon and post thermal annealing effects on the (GaIn)2O3 films deposited on sapphire substrates by pulsed laser deposition. Films grown at substrate temperature higher than 300°C showed phase separation while films grown at substrate temperature lower than 200°C revealed homogenous elements distributions with amorphous structure. Thermal annealing had no obvious effects on (GaIn)2O3 films grown at substrate temperature higher than 300°C. The clusters remained on the surface of the films after thermal annealing treatment. On the other hand, however, by thermal annealing the film deposited at room temperature, (GaIn)2O3 film with smooth surface, homogenous element distribution, high orientation crystal and high optical transmittance observed by means of scanning electron microscope, energy dispersive spectrometer, X-ray diffraction and spectrophotometer was successfully obtained, paving a way for obtaining high quality (GaIn)2O3 film without phase separation.

Resistive switching characteristics in dielectric/ferroelectric composite devices improved by post-thermal annealing at relatively low temperature

We have investigated the effects of post-thermal annealing on the resistive switching characteristics of dielectric/ferroelectric composite devices of SrRuO3/LaFeO3/Bi1−δFeO3/SrRuO3. Annealing of the devices above 85 °C enhanced the hysteresis of the current–voltage characteristics, resulting in an increase in the resistive switching ratio. After post-thermal annealing at 200 °C, devices with a thicker LaFeO3 layer exhibited a larger resistive switching ratio, and the device-to-device variation in the resistive switching ratio decreased as the LaFeO3-layer thickness was increased. The pulsed-voltage-induced resistive switching characteristics, such as the resistive switching ratio and the switching speed, were also improved by post-thermal annealing.

Advanced nanomechanics in the TEM: effects of thermal annealing on FIB prepared Cu samples

The effect of focused ion beam (FIB) fabrication on the mechanical properties of miniaturized mechanical tests has recently been realized, but is not well documented. In this study, the effect of post thermal annealing on the plastic properties of FIB fabricated micro- and nanometer-sized Cu samples was studied by means of advanced analytic and in situ transmission electron microscopy. In situ heating experiments on thin films and pillars revealed a reduction of the initially high dislocation density, but never a recovery of the bulk dislocation density. Aberration-corrected atomic imaging documented the recovery of a pristine crystalline surface structure upon annealing, while electron energy-loss spectroscopy showed that the remaining contamination layer consisted of amorphous carbon. These structural observations were combined with the mechanical data from in situ tests of annealed micro- and nanometer-sized tensile and compression samples. The thermal annealing in the micron regime mainly influences the initial yield point, as it reduces the number of suited dislocation sources, while the flow behavior is mostly unaffected. For the submicron samples, the annealed material sustains significantly higher stresses throughout the deformation. This is explained by the high stresses required for surface-mediated dislocation nucleation of the annealed material at the nanoscale. In the present case, the FIB affected the surface near defects and facilitated dislocation nucleation, thereby lowering the material strength.

Effect of post-thermal annealing on the structural and optical properties of ZnO thin films prepared from a polymer precursor

ZnO thin films were synthesised by a new method which uses polyvinyl alcohol (PVA) as the polymer precursor. The films are annealed at different temperatures and for different annealing times. The structural parameters, like grain size, lattice constants, optical band gap, and Urbach energy, depend on the annealing temperature and time. All the films possess tensile strain, which relaxes as the annealing temperature and time increase. The photoluminescence (PL) spectra contain only ultraviolet (UV) peaks at low temperature, but as the annealing temperature and time increase, we observe peaks at the blue and green regions with a variation in the intensities of these peaks with annealing temperature and time.

The effects of post-thermal annealing on the optical parameters of indium-doped ZnO thin films

Indium-doped ZnO thin films are deposited on quartz glass slides by RF magnetron sputtering at ambient temperature. The as-deposited films are annealed at different temperatures from 400 °C to 800 °C in air for 1 h. Transmittance spectra are used to determine the optical parameters and the thicknesses of the films before and after annealing using a nonlinear programming method, and the effects of the annealing temperatures on the optical parameters and the thickness are investigated. The optical band gap is determined from the absorption coefficient. The calculated results show that the film thickness and optical parameters both increase first and then decrease with increasing annealing temperature from 400 °C to 800 °C. The band gap of the as-deposited ZnO:In thin film is 3.28 eV, and it decreases to 3.17 eV after annealing at 400 °C. Then the band gap increases from 3.17 eV to 3.23 eV with increasing annealing temperature from 400 °C to 800 °C.

Post-thermal Annealing Effects on Photoluminescence Properties of InAs Quantum Dots on GaNAs Buffer Layer

The thermal annealing characteristics of InAs quantum dots (QDs) on a GaNAs buffer layer grown by the metalorganic chemical vapor deposition were investigated. Although the photoluminescence efficiency was deteriorated by annealing, the improved tolerance in the annealing time and temperature was confirmed in comparison with the GaAs buffer sample. The wavelength blue shift was similar in both buffer layers. The improvements in the PL efficiency were considered to be related to the decreased coalescent QDs upon introducing the dilute-nitrogen into the buffer layer.

Post-thermal Annealing Effects on Photoluminescence Properties of InAs Quantum Dots on GaNAs Buffer Layer

The thermal annealing characteristics of InAs quantum dots (QDs) on a GaNAs buffer layer grown by the metalorganic chemical vapor deposition were investigated. Although the photoluminescence efficiency was deteriorated by annealing, the improved tolerance in the annealing time and temperature was confirmed in comparison with the GaAs buffer sample. The wavelength blue shift was similar in both buffer layers. The improvements in the PL efficiency were considered to be related to the decreased coalescent QDs upon introducing the dilute-nitrogen into the buffer layer.

Effect of Post-Thermal Annealing of Thin-Film Transistors with ZnO Channel Layer Fabricated by Atomic Layer Deposition

We investigated zinc oxide (ZnO) thin films fabricated by atomic layer deposition (ALD) for their application in thin-film transistors (TFTs). The fabricated TFTs were annealed at various temperatures in various ambient gases. The characteristics of TFTs annealed in oxygen ambient at the temperature of up to 400 °C indicated improvements with no degradation of subthreshold swing or large shift in threshold voltage. From the annealing temperature dependences of transfer characteristics and X-ray diffraction patterns, we found that the improvements in electrical characteristics are attributed to the crystalline modification of ZnO films. The TFTs annealed at 400 °C in O2 ambient indicate improved stability against the bias stress. Secondary ion mass spectrometry analysis revealed a marked decrease in the hydrogen concentration of the ZnO channel layer after the annealing at 400 °C.

Stability Improvement of Gallium Indium Zinc Oxide Thin Film Transistors by Post-Thermal Annealing

The effects of post-thermal annealing on the stability of Ga2O3-In2O3-ZnO (GIZO) thin film transistors (TFT) were investigated by comparing the GIZO TFTs annealed for 3 hour and for 65 hours under high-field bias stress, light illumination, and long-term storage in air. We found that the poor stability of the GIZO TFTs under these stresses was remarkably improved after 65 hours' post-thermal annealing at 250 OC. The improvement of the stability is ascribed to the reduction of the trap sites in the GIZO layer and curing of weak atomic bonds otherwise susceptible to breaking during the stress.

Effects of Post Thermal Annealing on the Electrical Properties of Vertical Type Organic Thin Film Transistors Using Poly(3-hexylthiophene) and Its Application in Organic Light Emitting Transistor

We have fabricated the vertical type organic thin film transistor (OTFT) using electrically conductive poly(3-hexylthiophene) (P3HT) as a p-type organic material. Effects of post thermal annealing and thickness of active layer on the performance of vertical type transistors were investigated. Especially, the correlation between carrier mobility of P3HT after post thermal annealing and static characteristics of the transistor was studied. Carrier mobility was calculated by space charge limited current (SCLC) model from the I-V curves of the prepared device. The vertical type OTFT after post thermal annealing at 120 degrees C (Tg) showed high current of 0.383 mA and on-off ratio of 22.5 at a low gate voltage of +2.0 V. Additionally, we report on emission characteristics from the vertical type transistor using P3HT.

Characterization of Thermal Annealed n-ZnO/p-GaN/Al2O3

This paper reports the effects of post thermal annealing in air and N2 on the structural and optical properties of zinc oxide (ZnO) films deposited on a p-GaN substrate. The properties of annealed ZnO/GaN/Al2O3 films were investigated by atomic force microscopy (AFM), X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL), and Auger electron spectroscopy (AES). Our experiments demonstrated that the ZnO film annealed in N2 had better structural properties than as-deposited ZnO film. When annealed in air, the optical property of ZnO film was improved by the oxygen from ambient air, although the structural properties were somewhat poor and the interface of ZnO and GaN was degraded by the formation of a Ga–O mixed phase.

Effects of post-thermal annealing on the optical constants of ZnO thin film

ZnO thin film was deposited onto (0 0 0 1) sapphire substrate by a sol–gel method. The as-prepared film was annealed at different temperatures from 600 to 950 °C in argon ambient. Transmittance spectra were used to determine the optical constants of the annealed ZnO film, and the effects of the annealing temperature on the optical constants were investigated. Transmittance measurement shows that the absorption edge blueshifts when the annealing temperature is below 750 °C while redshifts when the annealing temperature exceeds 750 °C. With increasing the annealing temperature, the optical constant of ZnO film decreases in the ultraviolet region while increases in the visible region.

Formation of nickel silicide and germanosilicide layers on Si(001), relaxed SiGe∕Si(001), and strained Si/relaxed SiGe∕Si(001) and effect of postthermal annealing

This study compared the formation of nickel silicide or germanosilicide layers on various SiGe based heterostructures as well as the effects of the different annealing schemes (one-step versus two-step annealing) on the morphological, structural, and electrical properties. Uniform nickel silicide or germanosilicide layers were first formed by rapid thermal annealing of various heterostructures. The two-step annealing process of the samples first at 400°C (TA1) and subsequently at between 600 and 800°C (TA2) led to an increase in the sheet resistance, which was attributed to the formation of a high-resistivity NiSi2 phase, the agglomeration of the silicide or germanosilicide layers, and the formation of an amorphous interlayer between the silicide or germanosilicide layers. The lower sheet resistance of the silicide or germanosilicide layers formed on the relaxed-Si1−xGex (x=0.15)∕Si(001) substrates by two-step annealing compared with that of the samples formed on the strained Si/relaxed SiGe∕Si(001) and Si(001) was attributed to the suppression of the high-resistivity NiSi2 phase as well as the superior thermal stability of the germanosilicide layer formed on the relaxed Si1−xGex (x=0.15)∕Si(001). The amorphous interlayers formed in the samples annealed using two-step procedure appeared to suppress interface roughening between the silicide or germanosilicide and the SiGe layer presumably due to the reduced Ni and Ge diffusion rate. Here, an amorphous interlayer was formed, which was attributed to the large negative heat of mixing in Ni–Si–Ge systems during the phase transformation and grain growth.

The Effect of Thermal Treatment on Device Characteristic and Reliability for Sub-100-nm CMOSFETs

The effect of post-thermal annealing after halo implantation on device characteristic and reliability of sub-100-nm CMOSFETs was investigated. We found that the control of annealing time is more efficient than that of annealing temperature with respect to improving the hot-carrier-induced degradation. The best result of device performance and reliability was obtained by a post-thermal annealing treatment performed at medium temperatures (e.g., 900/spl deg/C) for a longer time (>1 min).