Effect Of Post-deposition Annealing Research Articles

Synthesis and effect of post-deposition thermal annealing on morphological and optical properties of ZnO thin film

Zinc oxide thin films have been deposited on glass substrates by the chemical bath deposition method; a surfactant, cetyltrimethylammonium bromide (CTAB); was used as capping agent. The films were annealed at two different temperatures: 200 and 300 °C. The structural features were investigated by X-ray diffraction analysis which exhibited hexagonal wurtzite structures along with c-axis orientations. Crystallite size was estimated and found to be around 33–41 nm. The effect of post-deposition thermal annealing on the morphological and optical properties has been investigated by scanning electron microscopy and photoluminescence spectra at room temperature. The band gap energies of uncapped and CTAB-capped ZnO films were found to be 3.28 and 3.48 eV, respectively.

Effect of Annealing in a Nitrogen Atmosphere on the Properties of In2O3 Films Deposited with RF Magnetron Sputtering

<TEX>$In_2O_3$</TEX> films were deposited by RF magnetron sputtering on a glass substrate and then the effect of post deposition annealing in nitrogen atmosphere on the structural, optical and electrical properties of the films was investigated. After deposition, the annealing process was conducted for 30 minutes at 200 and <TEX>$400^{\circ}C$</TEX>. XRD pattern analysis showed that the as deposited films were amorphous. When the annealing temperature reached 200-<TEX>$400^{\circ}C$</TEX>, the intensities of the <TEX>$In_2O_3$</TEX> (222) major peak increased and the full width at half maximum (FWHM) of the <TEX>$In_2O_3$</TEX> (222) peak decreased due to the crystallization. The films annealed at <TEX>$400^{\circ}C$</TEX> showed a grain size of 28 nm, which was larger than that of the as deposited amorphous films. The optical transmittance in the visible wavelength region also increased, while the electrical sheet resistance decreased. In this study, the films annealed at <TEX>$400^{\circ}C$</TEX> showed the highest optical transmittance of 76% and also showed the lowest sheet resistance of <TEX>$89{\Omega}/\Box$</TEX>. The figure of merit reached a maximum of <TEX>$7.2{\times}10^{-4}{\Omega}^{-1}$</TEX> for the films annealed at <TEX>$400^{\circ}C$</TEX>. The effect of the annealing on the work-function of <TEX>$In_2O_3$</TEX> films was considered. The work-function obtained from annealed films at <TEX>$400^{\circ}C$</TEX> was 7.0eV. Thus, the annealed <TEX>$In_2O_3$</TEX> films are an alternative to ITO films for use as transparent anodes in OLEDs.

Influence of post-deposition annealing on structural, optical and electrical characteristics of NiO/ZnO thin film hetero-junction

ABSTRACTTransparent p-n hetero-junction diodes are fabricated using, p-type NiO and n-type ZnO thin films deposited onto a Pt/Ti/glass substrate utilizing RF sputtering technique. The prepared hetero-junctions are studied for the structural, electrical and optical properties and the effect of post-deposition annealing is investigated through I-V measurements and XRD analysis. The as deposited hetero-junction is found to be giving ohmic behaviour while with post-annealing treatment it result in rectification with a ratio of forward-to-reverse current as high as 15 in the range -1.0 to 1.0 V. Forward threshold and the reverse breakdown voltages are found to be about 0.5 and -2.7 V, respectively. The forward-bias I-V characteristics are dominated by the flow of space-charge-limited current with an optical transmission of above 50 % in the visible region important for the transparent electronic device fabrication.

Properties of Atomic Layer Deposited HfO2 Films on Ge Substrates Depending on Process Temperatures

The effect of deposition temperature and post deposition annealing (PDA) on the electrical properties of HfO2 films grown on a Ge substrate by atomic layer deposition (ALD) was investigated. The HfO2 films deposited at 280°C (280°C-HfO2) showed a large capacitance-voltage (C-V) hysteresis, but it was significantly reduced at 200°C (200°C-HfO2). Further reduction of deposition temperature to 160°C resulted in the abrupt increase of C-V hysteresis. The reduction of C-V hysteresis was originated from the smaller degree of intermixing between the HfO2 and Ge substrate with decreasing temperature, while the increase of C-V hysteresis comes from the low density of films grown at low temperatures. The C-V hysteresis characteristics were also strongly influenced by PDA temperatures. PDA temperatures higher than 550°C induced a large C-V hysteresis regardless of deposition temperature. Interestingly, after the PDA process, the HfO2 grown at 200°C is crystallized to the tetragonal phase, while the HfO2 grown at 280°C is crystallized to the monoclinic phase. These different crystalline phases result in a lower equivalent oxide thickness in the 200°C-HfO2 compared to the 280°C-HfO2

Effect of high temperature annealing on the performance of MANOS charge trapping memory

We have investigated the effect of post deposition annealing (PDA) temperature of Al2O3 blocking layer on the performance of charge trapping memory capacitors. Two splits of PDA were performed in N2 ambient at 850°C/60 s and 1050°C/60 s, respectively. The 1050°C annealed capacitor could be programmed and erased normally by using Fowler-Nordheim (FN) injection. In contrast, the 850°C annealed device could not be erased, even though it could be programmed properly. By measuring the gate leakage current and the flatband voltage shift, we found the erase failure in the 850°C annealed device was due to a larger gate back-injection leakage current at V g<0. The trend of gate leakage current was further verified in two Al/Al2O3/SiO2/p-Si control capacitors with the same PDA splits. In addition, constant voltage stress measurements on control capacitors in the FN regime showed that the change of gate leakage current followed an empirical Curie-von Schweidler law at V g<0. The data pointed out the importance to further study the relation between PDA conditions and the defect generation properties in Al2O3 blocking layer.

Effect of the post-deposition annealing on electrical characteristics of MIS structures with HfO2/SiO2 gate dielectric stacks

Abstract In this work, we report on effects of post-deposition annealing on electrical characteristics of metal–insulator–semiconductor (MIS) structures with HfO2/SiO2 double gate dielectric stacks. Obtained results have shown the deterioration of electro-physical properties of MIS structures, e.g. higher interface traps density in the middle of silicon forbidden band (Ditmb), as well as non-uniform distribution and decrease of breakdown voltage (Ubr) values, after annealing above 400 °C. Two potential hypothesis of such behavior were proposed: the formation of interfacial layer between hafnia and silicon dioxide and the increase of crystallinity of HfO2 due to the high temperature treatment. Furthermore, the analysis of conduction mechanisms in investigated stacks revealed Poole–Frenkel (P–F) tunneling at broad range of electric field intensity.

Deposition and post-deposition annealing of thin Y 2O 3 film on n-type Si in argon ambient

Thin (∼5.0 nm) Y 2O 3 films were deposited on n-type Si (1 0 0) substrate using RF magnetron sputtering. Detailed studies on the effects of post-deposition annealing (PDA) temperatures (400, 600, 800, and 1000 °C) in argon ambient on these films were performed by X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), field emission scanning electron microscopy, and atomic force microscopy. Interfacial layer (IL) of SiO 2 in between Y 2O 3 and the Si substrate for sample annealed from 400 to 800 °C had been suggested from the results of FTIR. As for sample annealed at 1000 °C, presence of IL might consist of both Y 2Si 2O 7 and/or SiO 2 through the detection of Y 2Si 2O 7 compound and Si–O chemical bonding from XRD and FTIR analysis, respectively. For as-deposited sample, no detectable chemical functional group at the IL was recorded. Electrical characteristics of the Y 2O 3 films were acquired by fabricating metal-oxide–semiconductor capacitor as test structure. An improvement in the breakdown voltage ( V B) and leakage current density ( J) was perceived as the PDA temperature increased. Of the PDA samples, the attainment of the lowest effective oxide charge, interface trap density, total interface trap density, and the highest barrier height at 1000 °C had contributed to the acquisition of the highest V B and lowest J.

Effect of annealing on the microstructure of NiFe 1.925Dy 0.075O 4 thin films

Dysprosium-doped nickel-ferrite (NiFe 1.925Dy 0.075O 4) thin films were fabricated using RF sputter-deposition. Structural studies indicate that the effect of post-deposition annealing is significant on structural evolution in NiFe 1.925Dy 0.075O 4 films. As-grown NiFe 1.925Dy 0.075O 4 films were amorphous. Annealing (T a) in air at 450–1000 °C results in the formation of nanocrystalline NiFe 1.925Dy 0.075O 4 films, which crystallize in the inverse spinel structure. The average grain size ( L) increases from 5 to 40 nm with increasing T a from 450 to 1000 °C. Lattice constant of NiFe 1.925Dy 0.075O 4 films is higher compared to that of NiFe 2O 4 due to partial substitution of Dy 3+ ions for Fe 3+ ions. The lattice parameter increases from 8.353 to 8.362 Å with increasing T a from 450 to 1000 °C which is attributed to the lattice-strain developed in the NiFe 1.925Dy 0.075O 4 films with increasing T a. The corresponding density of NiFe 1.925Dy 0.075O 4 films increases from 3.2 to 3.9 g/cm 3 with increasing annealing temperature. Magnetization measurements indicate the ferromagnetic behavior of all the films while the coercive field values at 300 K are found to be 0.0134 T and 0.0162 T for as grown and T a = 1000 °C films, respectively.

Effects of post-deposition rapid thermal annealing on aluminum-doped ZnO thin films grown by atomic layer deposition

Aluminum-doped ZnO (AZO) thin films with alternating stacks of ZnO and Al 2O 3 were grown by atomic layer deposition (ALD) on c-face sapphire substrates. Post-deposition rapid thermal annealing (RTA) at 950 °C for 5 min was conducted in all AZO samples. The X-ray diffraction patterns demonstrate that the intensity of cubic ZnAl 2O 4 (3 1 1) peaks grow with the increase of Al content, which implies the diffusion of Al atoms into ZnO. The reduction of dominant peak intensity of cubic ZnO (1 1 1) and the increase of hexagonal ZnO (1 0 0) and (1 0 1) peaks intensity suggest that there were variations of crystal structures for the samples with Al content above 6%. Two orders of magnitude of electron concentration raises in samples with 2 and 4% Al content compared with the as-grown without RTA-treated samples. It also infers that RTA facilitates diffusion of Al atoms in AZO material structures and activation of Al dopants. When Al content is above 6%, the variations of crystal structures with the enhancement of biaxial compressive strain result in blue shift in energy of photoluminescence peak and in frequency of E 2 high phonon mode of micro-Raman spectra. The deterioration of crystal quality due to the increase of strain-induced defects hinders the electrical and optical performance when Al doping concentration is above 6% in AZO materials.

Effect of deposition parameters and post-deposition annealing on the morphology and cellular response of electrosprayed TiO2 films

Titania films (TiO2) were deposited on Ti alloy substrates by electrohydrodynamic atomization (EHDA), also called electrospraying, and the morphology and phase composition of the coatings were evaluated. A range of TiO2 sols (2–8 wt%) were prepared via the hydrolysis of polymeric precursors using isopropanol (prOH) as a solvent carrier. Stable cone-jet formation during the EHDA process was greatly influenced by varying the liquid physical properties. Deposition parameters such as sol concentration, needle-to-substrate distance and spray time were found to affect film morphology. Dense and continuous films were obtained under optimized conditions whereby a 2 wt% TiO2 sol was atomized at a flow rate of 5 µl min−1 by a needle of 300 µm inner diameter, kept at a distance of 20 mm from the grounded substrate and operating at an applied voltage of 3.5–4.2 kV. The films were then crystallized by heating to 300–600 °C. Annealing increased the hydrophilicity of the films but did not significantly affect the surface roughness of the films. In vitro cellular response was determined by studying the interaction between MG63 cells and the films annealed at the various temperatures. MG63 cells were able to grow and proliferate on all the TiO2 films, while the highest proliferation rate was found on the TiO2 films annealed at 600 °C. Our results indicate that electrosprayed TiO2 films possess great potential for biomedical applications.

CdS thin film post-annealing and Te–S interdiffusion in a CdTe/CdS solar cell

Small area CdTe/CdS solar cells were fabricated using chemical bath deposited CdS and CSS deposited CdTe thin films to investigate the interface properties related to the CdS processing. The effect of post deposition annealing of CdS on the junction properties and the possible interdiffusion at the interface is discussed. The hypothesis of hardening of CdS due to annealing against the diffusion of “S” and “Te” is discussed using the quantum efficiency data in the blue and red regions. Devices prepared using as-deposited CdS films exhibited evidences of higher “S” and “Te” diffusion compared to devices made using CdS films annealed in oxygen. The maximum efficiency of the devices used in this study was 9.8%.

Roles of thermal annealing in cyclopentadithiophene/thienopyrroledione:fullerene blended film and performance of organic photovoltaics

The authors have attentively investigated the roles of the thermal annealing in the thin blended film of a novel low band-gap polymer poly[(4,4-bis(2-ethyl)cyclopenta- [2,1-b:3,4-b’]dithiophene)-2,6-diyl-alt-(5-octylthieo[3,4-b]pyrrole-4,6-dione)-1,3-diyl] (PCPDTTPD) and [6,6]-phenyl C 60 butyric acid methyl ester (PCBM). The surface morphology, optical absorption spectra and carrier mobility of the PCPDTTPD:PCBM film as a function of annealing temperature were investigated. Open-circuit voltage as high as 0.86 V was obtained in the PCPDTTPD:PCBM active layer based organic photovoltaics. The post-deposition annealing effects on the performance of solar cells also have been discussed. The results illustrated that the maximum power conversion efficiency of 2.01% was achieved in the as-cast devices.

Effect of postdeposition annealing on the structural and electrical properties of thin Dy 2TiO 5 dielectrics

This paper describes the effect of postdeposition annealing on the structural and electrical characteristics of high-k Dy 2TiO 5 dielectric films deposited on Si (100) through reactive cosputtering. We used X-ray diffraction, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and atomic force microscopy to investigate the structural and morphological features of these films after they had been subjected to annealing at different temperatures. The Dy 2TiO 5 dielectrics annealed at 800 °C exhibited excellent electrical properties such as high capacitance value, small density of interface state, almost no hysteresis voltage, and low leakage current. This phenomenon is attributed to a rather well-crystallized Dy 2TiO 5 structure and the reduction of the interfacial layer at oxide/Si interface. This film also shows almost negligible charge trapping under high constant voltage stress.

Structural, optical, and electrical properties of E-beam and sputter-deposited ITO films for LED applications

The structural, electrical, and optical properties of e-beam and sputter-deposited Indium-Tin-Oxide (ITO) films on sapphire and p-GaN wafers, as well as the post-deposition annealing effect for light-emitting-diode applications, were analyzed and compared. The specific contact resistance of the sputtered ITO film on a p-GaN wafer was found to be slightly higher than that of the e-beam deposited ITO films. However, in general, the electrical, structural and optical properties of the sputtered ITO films that were annealed at comparably lower temperature are better than those of the e-beam deposited ITO films, which is the consequence of a larger average grain size. The sputtered ITO film that was annealed at 500°C demonstrated a resistivity of as low as 3.6 × 10−4 Ω·cm, along with a high transmittance of ∼98% at 450 nm.

Effect of high temperature annealing on tunnel oxide properties in TANOS devices

We investigate the effect of high temperature Post-Deposition Annealing of Al 2O 3 on the tunnel oxide of TANOS-like non-volatile memories. We found that, when temperature steps above 850 °C are applied after the stack deposition, a transition layer is forming by the intermixing of the Si 3N 4 with the upper part of the underneath SiO 2. We found that this transition layer has worse dielectric properties as compared to SiO 2, altering in a not-negligible way the performance of TANOS memories, and in particular severely penalizing retention.

Effects of N2O Postdeposition Annealing on Metal-Organic Decomposed CeO2 Gate Oxide Spin-Coated on GaN Substrate

Effects of postdeposition annealing (PDA) in N2O ambient on metal-organic decomposed CeO2 films deposited on GaN substrate had been reported. The utilization of N2O gas during PDA had successfully suppressed the decomposition of GaN as revealed by x-ray diffraction (XRD). XRD had detected the presence of CeO2 and α-Ce2O3 phases, wherein the phase transformation of CeO2 to α-Ce2O3 led to the formation of β-Ga2O3 interfacial layer (IL). Formation of IL comprising of Ga–O and Ga–O–N compounds in CeO2/GaN system was verified by dark-field scanning transmission electron microscope image and energy dispersive x-ray line profile, respectively. The metal–oxide–semiconductor characteristics of CeO2/GaN structure showed a change of negative to positive effective oxide charge (Qeff) and increasing interface-trap density (Dit) as a function of PDA temperature. The highest oxide breakdown field demonstrated by 1000°C-annealed sample was correlated with Qeff and Dit. A detailed explanation on this correlation as well as current transport mechanism in these oxides has been presented.

Effects of Oxygen and Forming Gas Annealing on ZnO TFTs

ABSTRACTZnO TFTs with bottom gate top S/D contact architecture were fabricated by sputtering of ZnO with layer thicknesses from 30 nm to 100 nm. The effect of post deposition annealing in oxygen and forming gas atmospheres at 400°C to 500°C on the devices was investigated. The tendencies of a lower threshold voltage Vth and a higher saturation mobility μsat for higher annealing temperature can be observed for both oxygen and forming gas annealing. Reduction of trap density in oxygen annealing and additional hydrogen incorporation in forming gas annealing play an important role for these electrical parameters. Morphological changes of increased grain size and fewer grain boundaries in the channel also contribute to tendencies in electrical characteristics of ZnO TFTs.

The Effects of Postdeposition Annealing on the Crystallization and Electrical Characteristics of HfO2 and ZrO2 Gate Dielectrics

This study examined the effects of postdeposition annealing (PDA) on the electrical characteristics of atomic layer deposited ZrO2 and HfO2 films using similar precursors and process conditions. After PDA at 600oC, the insulating properties of ZrO2 improved but those of HfO2 deteriorated. The improved insulating properties of ZrO2 were attributed to the negligible increase in the interfacial layer thickness and an amorphous to tetragonal phase transformation. In addition, the degraded insulating properties of HfO2 after PDA at high temperatures were attributed to an abrupt increase in the interfacial layer thickness and the generation of conducting paths through the grain boundaries.

Nonvolatile and unipolar resistive switching characteristics of pulsed laser ablated NiO films

Unipolar nonvolatile resistive switching memory properties of pulse laser ablated nickel oxide films have been studied. Grazing incidence x-ray diffraction and electron diffraction spectra of the oxide films reveal polycrystalline nature of deposited NiO films. Cross-sectional transmission electron micrograph shows a fairly uniform oxide surface. The rms surface roughnesses of deposited oxides have been studied as a function of annealing temperature using atomic force microscopy. By applying a proper voltage bias and compliance, Pt/NiO/Pt structures exhibited unipolar resistive switching having a very low SET and RESET voltages. The OFF state resistance and SET voltage are found to increase with the increase in annealing temperature. The ratio between the two resistance states can be as high as 1000. The current conduction phenomena at two resistance states have been studied. The switching phenomena have been explained using the rupture and formation of conducting filaments. The effect of postdeposition annealing on the resistance switching properties is discussed.

EFFECT OF POST-DEPOSITION ANNEALING IN FORMING GAS ON STRUCTURAL AND ELECTRICAL PROPERTIES OF SOL–GEL DERIVED SiO2 THICK FILM ON 4H–SiC

The effect of post-deposition annealing in forming gas on the structural and electrical properties of sol–gel derived SiO 2 thick film on n-type 4H–SiC has been systematically investigated. Tetraethylorthosilicate-based precursor with H 2 SO 4 as catalyst was prepared and prior to film deposition, substrate surface was treated by hexamethyldisilizane. The spin-coated film was annealed at 750–950°C for 30 min with an approximately 185-nm thick film. It was found that oxide annealed at the highest temperature revealed the densest film, lowest oxide defects, and lowest total interface trap density. As a result, this oxide had demonstrated the lowest leakage current density if compared with other oxides.