Impact Of Post-deposition Annealing Research Articles

Investigation of ALD HfSiOx as gate dielectric on β -Ga2O3 (001)

The interface and bulk properties of ∼20 nm hafnium-silicon-oxide (HfSiOx) dielectric deposited by atomic layer deposition (ALD) on (001) β-Ga2O3 were investigated systematically using deep ultraviolet photo-assisted capacitance–voltage (C–V) and current–voltage (I–V) measurements. The ALD HfSiOx dielectric constant, bulk, and HfSiOx/Ga2O3 interface quality and breakdown field were determined, and the impact of post-deposition annealing (PDA) on these parameters was studied. PDA reduced near-interface traps resulting in a smaller hysteresis without changing the dielectric constant. An average trap density of 2.72 × 1012 and 1.06 × 1012 cm−2 eV−1 was measured on samples with PDA at 400 and 900 °C, respectively. In addition, a high dielectric constant of 9.28 and breakdown field as high as 8.7 MV/cm were achieved on these devices.

Impact of post-deposition annealing on the optical, electrical, and structural properties of CdS thin films for solar cell applications

In this study thermally evaporated cadmium Sulfide (CdS) thin films with the thickness of 100 nm were fabricated at 150 °C under the pressure of 2 × 10−5 mbar and subjected to annealing treatment at various temperatures. The optical, electrical, and structural properties of CdS thin films, which were influenced by annealing treatment, were then studied using ultraviolet–visible (UV–Vis) spectroscopy, Hall effect measurement system, X-ray diffraction (XRD), Raman spectroscopy and Atomic force microscopy (AFM) analysis. The energy band gap was found to decrease from 2.402 eV for the as-grown CdS film to 2.250 eV for the film annealed at 450 °C. The electrical parameters of CdS thin films, such as carrier concentration, resistivity and mobility, were then calculated using the Hall effect measurement system; these were improved with the increase of the annealing temperature up to 350 °C. The crystallite size of the preferred (111) orientation was in the range of 12–40 nm and increased with annealing temperature. The increase in the intensity of peaks and shifting peaks toward the single-crystal mode was observed in the Raman spectra of the annealed CdS thin films. The AFM images also revealed that the film roughness increased with heat treatment. Further, the obtained SEM images showed the uniform surface of the film. The efficiency of the designed solar cell was in the range of 21.84–22.18 %; it was increased by using the annealed CdS films. The present work, thus, introduced the annealed CdS thin film at 350 °C as a promising window layer to fabricate highly efficient CdTe-based solar cells.

Impact of post-deposition annealing on the electronic properties of Al2O3/GaN interface by first-principles study

The electronic properties of Al2O3/GaN interface are investigated by first-principles calculations to explore the effects of post-deposition annealing (PDA) in O2 or N2 ambient. It is found that for the initial Al2O3/GaN interface without post-annealing, there are traps with a wide energy range in the GaN band gap, mainly caused by dangling bonds (DBs) of Ga, Al, and N atoms. However, with proper PDA in O2 ambient, the trap states induced by Al DBs completely merge into GaN conduction band, while the trap states induced by Ga DBs and N DBs completely merge into GaN valence band. Therefore, the interface shows a cleaner band structure. Nevertheless, excessive interface O content can lead to trap states around the valence band maximum induced by N DBs and O DBs. For PDA in N2 ambient, the trap states induced by Al DBs and Ga DBs can be completely suppressed under appropriate interface N content. Unfortunately, deep and shallow traps caused by N DBs can be introduced in the GaN band gap. This study systematically reveals the physical mechanism by which PDA in O2 ambient compared to N2 can significantly reduce the interface state density and improve threshold voltage stability of the device.

Effect of Annealing on Resistive Switching Properties of Glancing Angle Deposition‐Assisted WO3 Thin Films

Herein, the impact of postdeposition annealing on resistive switching behavior of radio frequency magnetron sputtered WO3 thin films is reported. Films are deposited under glancing angle deposition (GLAD) configuration of sputtering at varying GLAD angle from 65° to 80°. Structure transition from monoclinic to orthorhombic phase in deposited WO3 films is perceived after ex situ annealing at temperature of 400 °C. Resistive switching properties show shift from bipolar to unipolar switching on postdeposition annealing. WO3 films show unipolar switching behavior after ex situ annealing for all prepared samples. The value of resistance in high resistance state is lowered after ex situ heating treatment and interestingly switching voltage also reduces to 3 V from 7 V after annealing treatment. The ratio of high to low resistance state for annealed WO3 film fabricated at 70° GLAD angle is achieved to be maximum (≈219). A detailed charge transport mechanism shows that ohmic behavior is dominant current conduction mechanism at lower applied voltage, while space charge limited current and Child's law are dominant at higher applied voltages. Obtained results encourage utilization of prepared WO3 thin films toward a wide variety of applications in optoelectronics, microelectronics, and environmental engineering along with advanced electronics such as resistive memory devices.

Structural and Sensing Characteristics of NiOx Sensing Films for Extended-Gate Field-Effect Transistor pH Sensors

In this article, the impact of post-deposition annealing (PDA) on the structural features and sensing properties of the NiOx sensing films deposited on a n+-type Si substrate was studied for an extended-gate field-effect transistor (EGFET) pH sensor. X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscope, and transmission electron microscopy were applied to explore the crystal structure, elemental composition, film morphology, and film microstructure of the NiOx sensing films after PDA at five different temperatures, respectively. The NiOx sensing film after PDA at 500 °C showed a higher pH sensitivity of 60.65 mV/pH, a smaller hysteresis width of 1.8 mV and a lower drift coefficient of 0.28 mV/h than those at different PDA temperatures. This result may be attributable to the promoted proton-exchange process and increased the number of surface bind-sites due to the NiOx film featuring the column-like polycrystalline structure, possessing a high Ni2+ content and forming of a thinner silicide layer at the NiOx/Si interface. In addition, this PDA temperature can minimize the oxygen vacancies and passivate the trap sites, thus reducing the formation of a hydrated layer on the NiOx film surface.

Tuning of oxygen vacancy-induced electrical conductivity in Ti-doped hematite films and its impact on photoelectrochemical water splitting

Titanium (Ti)-doped hematite (α-Fe2O3) films were grown in oxygen-depleted condition by using the spray pyrolysis technique. The impact of post-deposition annealing in oxygen-rich condition on both the conductivity and water splitting efficiency was investigated. The X-ray diffraction pattern revealed that the films are of rhombohedral α-Fe2O3 structure and dominantly directed along (012). The as-grown films were found to be highly conductive with electrons as the majority charge carriers (n-type), a carrier concentration of 1.09×1020 cm−3, and a resistivity of 5.9×10−2 Ω-cm. The conductivity of the films were reduced upon post-deposition annealing. The origin of the conductivity was attributed firstly to Ti4+ substituting Fe3+ and secondly to the ionized oxygen vacancies (VO) in the crystal lattice of hematite. Upon annealing the samples in oxygen-rich condition, VO slowly depleted and the conductivity reduced. The photocurrent of the as-grown samples was found to be 3.4 mA/cm−2 at 1.23 V vs. RHE. The solar-to-hydrogen efficiency for the as-grown sample was calculated to be 4.18% at 1.23 V vs. RHE. The photocurrents were found to be significantly stable in aqueous environment. A linear relationship between conductivity and water-splitting efficiency was established.

Impact of post-deposition annealing in Cu2SnS3 thin film solar cells prepared by doctor blade method

In this work, post-deposition annealing is done at three different temperatures on Cu2SnS3 (CTS) thin film solar cells prepared by doctor blade technique. Structural and electrical characteristics are determined from scanning electron microscopy (SEM), energy-dispersive X-ray fluorescence spectroscopy (ED-XRF), X-ray diffraction (XRD), Hall Effect and I-V characteristics studies to enlighten the mechanisms by which solar cells performance varies. The highest efficiency gain is obtained 1.14%. It is concluded that the optimum post-deposition annealing temperature for CTS is 400 °C for 30 min in the sulfur atmosphere.

Impact of post-deposition annealing on RF sputtered calcium copper titanate thin film for memory application

Calcium copper titanate (CCTO) sputtering target was synthesized by solid state method. Structural analysis of target has confirmed the formation of CCTO phase. CCTO thin films were deposited by RF magnetron sputtering technique on p-Si (100) substrates with the working pressure and RF power of 5 × 10–3 mbar and 105 W, respectively. Post-deposition annealing was performed at different temperatures ranging from 650 °C to 950 °C. Evolution of CCTO polycrystalline peaks has been observed in the 950 °C annealed film. The formation of CCTO phase has also been confirmed by FTIR spectroscopy studies. The surface morphology of the annealed thin film was found to be modulated with the annealing temperature. Larger microstructures have been found for the films annealed at high temperature. Bandgap of films were calculated from UV–vis spectral analysis. Electrical properties of the annealed thin films were studied by fabricating Al/CCTO/Si MOS structures. The interface trap density (Dit) was calculated as 7.9 × 1010 eV−1 cm−2 for the films annealed at 950 °C. Improved bipolar resistive switching behavior has been observed for the films annealed at 950 °C.

Interface trapping in (2¯01) β-Ga2O3 MOS capacitors with deposited dielectrics

The electrical properties of interfaces and the impact of post-deposition annealing have been investigated in gate oxides formed by low pressure chemical vapor deposition (LPCVD SiO2) and atomic layer deposition (Al2O3) on (2¯01) oriented n-type β-Ga2O3 single crystals. Capacitance-voltage based methods have been used to extract the interface state densities, including densities of slow ‘border’ traps at the dielectric-Ga2O3 interfaces. It was observed that SiO2-β-Ga2O3 has a higher interface and border trap density than the Al2O3-β-Ga2O3. An increase in shallow interface states was also observed at the Al2O3-β-Ga2O3 interface after post-deposition annealing at higher temperature suggesting the high temperature annealing to be detrimental for Al2O3-Ga2O3 interfaces. Among the different dielectrics studied, LPCVD SiO2 was found to have the lowest dielectric leakage and the highest breakdown field, consistent with a higher conduction band-offset. These results are important for the processing of high performance β-Ga2O3 MOS devices as these factors will critically impact channel transport, threshold voltage stability, and device reliability.

Raman scattering analysis of the surface chemistry of kesterites: Impact of post-deposition annealing and Cu/Zn reordering on solar cell performance

Post-deposition annealing (PDA) of chalcogenide-based solar cells has shown to enhance optoelectronic properties, though the mechanism for such improvement is still poorly understood. In this work Cu2ZnSnSe4 kesterite-based solar cells are fabricated and subjected to different PDA temperatures in order to study the structure/function relationships and explain the responsible mechanisms. Diffusion and recrystallization phenomena at the absorber/buffer interface during the PDA are investigated using multiwavelength Raman spectroscopy and photoluminescence, and correlated to the optoelectronic properties. By using varying laser excitations (442, 532, 785nm), the selective acquisition of structural information at different depths is obtained, thus providing insights of the differences in the composition and defect concentration in the device cross section. The results show that PDA treatments of completed devices induce a redistribution of atoms (Cu and Zn) within the surface and sub-surface of the absorber layer. The absorber surface becomes more Cu-depleted and Zn-enriched, creating optoelectronically beneficial defects VCu and ZnCu, which are partly responsible for the performance improvement. Recrystallization effects of the CdS layer are observed, leading to a better absorber-buffer interface and potentially a better band alignment. Additionally, this work opens the possibility of tuning the defect concentration in the absorber with the PDA temperature.

Impact of Postdeposition Annealing Ambient on the Mobility of Ge nMOSFETs With 1-nm EOT Al2O3/GeOx/Ge Gate-Stacks

The impact of postdeposition annealing (PDA) ambient on electrical properties of thin equivalent oxide thickness (EOT) Al2O3/GeO x /Ge gate-stacks is investigated. It is found that the surface states inside the conduction band of Ge are significantly suppressed by 40% through PDA with atomic deuterium ambient. As a result, enhancement of the effective mobility in the Ge nMOSFETs is realized in high normal field region. The electron mobility of 396 cm2/Vs is achieved at $N_{s}$ of $10^{13}$ cm $^{-2}$ with small EOT of $\sim 1$ nm, which is similar to the highest mobility reported so far at such small EOT range.

Investigation of Lanthanum Silicate Conditions on 4H-SiC MOSFET Characteristics

The lanthanum silicate interface engineering has been shown to dramatically improve the mobility of 4H-silicon carbide (SiC) MOSFETs. We studied the impact of post deposition annealing (PDA) conditions and the initial lanthanum oxide (La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) thickness on the MOSFET performance. The combination of 900 °C PDA and 1 nm La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> leads to highest field-effect mobility. Higher PDA temperature leads to mobility reduction due to lower lanthanum concentration at the SiC/dielectric interface. The peak mobility and threshold voltage show strong dependence on the initial La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> thickness.

Impact of post-deposition annealing on interfacial chemical bonding states between AlGaN and ZrO2 grown by atomic layer deposition

The effect of post-deposition annealing on chemical bonding states at interface between Al0.5Ga0.5N and ZrO2 grown by atomic layer deposition (ALD) is studied by angle-resolved x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that both of Al-O/Al 2p and Ga-O/Ga 3d area ratio decrease at annealing temperatures lower than 500 °C, which could be attributed to “clean up” effect of ALD-ZrO2 on AlGaN. Compared to Ga spectra, a much larger decrease in Al-O/Al 2p ratio at a smaller take-off angle θ is observed, which indicates higher effectiveness of the passivation of Al-O bond than Ga-O bond through “clean up” effect near the interface. However, degradation of ZrO2/AlGaN interface quality due to re-oxidation at higher annealing temperature (&amp;gt;500 °C) is also found. The XPS spectra clearly reveal that Al atoms at ZrO2/AlGaN interface are easier to get oxidized as compared with Ga atoms.

Impact of post deposition annealing in the electrically active traps at the interface between Ge(001) substrates and LaGeOx films grown by molecular beam deposition

Changes in the electron trapping at the interface between Ge substrates and LaGeOx films grown by atomic O assisted molecular beam deposition are inferred upon post deposition annealing treatment on the as-deposited films from electrically detected magnetic resonance (EDMR) spectroscopy and from the electrical response of Pt/LaGeOx/Ge metal oxide semiconductor (MOS) capacitors. The improved electrical performance of the MOS capacitors upon annealing is consistent with the EDMR detected reduction of oxide defects which are associated with GeO species in the LaGeOx layer as evidenced by x-ray photoelectron spectroscopy.

Impact of post-deposition annealing on surface, bulk and interface properties of RF sputtered AlN films

C axis oriented AlN films were deposited on silicon substrate by radio frequency reactive magnetron sputtering. Subsequently the films were annealed in a horizontal furnace at temperatures ranging from 400 to 800°C for 30 min in nitrogen ambient. The change in the morphological properties with annealing temperatures was investigated using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and atomic force microscopy techniques. Morphological studies revealed that the annealing increased surface roughness and grain size. In addition, Al–N bond density along with the crystallinity of the deposited films was improved with annealing. The electrical properties, namely the insulator charge density (Qin) and the interface electronic state density (Dit), were estimated by the capacitance–voltage (C–V) measurements. It was found that the Qin increased, but the Dit decreased with annealing temperature. Lower leakage current with improved resistivity and dielectric behaviour was also observed with annealing.

Impact of Post Deposition Annealing on Characteristics of HfxZr1-xO2

AbstractIn this paper the impact of post deposition annealing in various ambient on electrical properties of hafnium zirconate (HfxZr1-xO2) high-k dielectrics is reported. ALD HfxZr1-xO2 films are annealed in a nitrogen and/or oxygen ambient at 500°C to 1000°C. Devices annealed at 500°C in N2 has lower equivalent oxide thickness (EOT) of 10Å without significant increase in gate leakage (Jg), threshold voltage (Vt) and only a slight decrease in transconductance (Gm) values compared to 500°C O2 annealed devices. Furthermore, the impact of annealing HfxZr1-xO2 films in a reducing ambient (NH3) is studied. Optimized NH3 anneal on HfxZr1-xO2 results in lower CET, improved PBTI, low sub-threshold swing values, comparable high-field Gm with only a minor degradation in peak Gm compared to control HfxZr1-xO2. Finally, the impact of laser annealing vs. RTP annealed HfxZr1-xO2 films are reported. Laser annealing helped further stabilize tetragonal phase of HfxZr1-xO2 without inducing void formation. Good devices with low leakage, low EOT and high mobility are obtained for laser annealed HfxZr1-xO2.