136 research outputs found
Influence of substrate bias on the structural and dielectrical properties of magnetron-sputtered BaxSr1-xTiO3 thin films
The application of a substrate bias during rf magnetron sputtering alters the
crystalline structure, grain morphology, lattice strain and composition of
BaxSr1-xTiO3 thin films. As a result, the dielectric properties of
Pt/BaxSr1-xTiO3/Pt parallel-plate capacitors change significantly. With
increasing substrate bias we observe a clear shift of the ferroelectric to
paraelectric phase transition towards higher temperature, an increase of the
dielectric permittivity and tunability at room temperature, and a deterioration
of the dielectric loss. To a large extent these changes correlate to a gradual
increase of the tensile in-plane film strain with substrate bias and an abrupt
change in film composition.Comment: 24 pages, 8 figures, submitted to Ferroelectric
Coating and functionalization of high density ion track structures by atomic layer deposition
In this study
flexible TiO
2
coated
porous
Kapton
membranes are presented having electron
multiplication properties. 800 nm crossing pores were fabricated into 50
m thick Kapton
membranes using ion track technology and chemical etching. Consecutively,
50 nm TiO
2
films were deposited i
nto
the pores of the
Kapton
membranes
by atomic layer deposition
using Ti(
i
OPr)
4
and water as precursors at 250 °C.
The TiO
2
films and coated membranes
were studied by scanning electro
n microscopy (SEM), X
-
ray diffraction (XRD) and X
-
ray
reflectometry (XRR). Au metal electrod
e fabrication onto both sides of the coated foils was
achieved by electron beam evaporation.
The
electron
multipliers were obtained by joining
3
two coated
membranes
separated by a conductive spacer.
The results show that electron
multiplication can be achie
ved using ALD
-
coated flexible
ion track polymer foils
Structural and Optical Characterization of ZnS Ultrathin Films Prepared by Low-Temperature ALD from Diethylzinc and 1.5-Pentanedithiol after Various Annealing Treatments
The structural and optical evolution of the ZnS thin films prepared by atomic layer deposition (ALD) from the diethylzinc (DEZ) and 1,5-pentanedithiol (PDT) as zinc and sulfur precursors was studied. A deposited ZnS layer (of about 60 nm) is amorphous, with a significant S excess. After annealing, the stoichiometry improved for annealing temperatures â„400 °C and annealing time â„2 h, and 1:1 stoichiometry was obtained when annealed at 500 °C for 4 h. ZnS crystallized into small crystallites (1â7 nm) with cubic sphalerite structure, which remained stable under the applied annealing conditions. The size of the crystallites (D) tended to decrease with annealing temperature, in agreement with the EDS data (decreased content of both S and Zn with annealing temperature); the D for samples annealed at 600 °C (for the time â€2 h) was always the smallest. Both reflectivity and ellipsometric spectra showed characteristics typical for quantum confinement (distinct dips/peaks in UV spectral region). It can thus be concluded that the amorphous ZnS layer obtained at a relatively low temperature (150 °C) from organic S precursor transformed into the layers built of small ZnS nanocrystals of cubic structure after annealing at a temperature range of 300â600 °C under Ar atmosphere
Structural and Optical Characterization of ZnS Ultrathin Films Prepared by Low-Temperature ALD from Diethylzinc and 1.5-Pentanedithiol after Various Annealing Treatments
The structural and optical evolution of the ZnS thin films prepared by atomic layer deposition (ALD) from the diethylzinc (DEZ) and 1,5-pentanedithiol (PDT) as zinc and sulfur precursors was studied. A deposited ZnS layer (of about 60 nm) is amorphous, with a significant S excess. After annealing, the stoichiometry improved for annealing temperatures â„400 °C and annealing time â„2 h, and 1:1 stoichiometry was obtained when annealed at 500 °C for 4 h. ZnS crystallized into small crystallites (1â7 nm) with cubic sphalerite structure, which remained stable under the applied annealing conditions. The size of the crystallites (D) tended to decrease with annealing temperature, in agreement with the EDS data (decreased content of both S and Zn with annealing temperature); the D for samples annealed at 600 °C (for the time â€2 h) was always the smallest. Both reflectivity and ellipsometric spectra showed characteristics typical for quantum confinement (distinct dips/peaks in UV spectral region). It can thus be concluded that the amorphous ZnS layer obtained at a relatively low temperature (150 °C) from organic S precursor transformed into the layers built of small ZnS nanocrystals of cubic structure after annealing at a temperature range of 300â600 °C under Ar atmosphere
Nanokapselien orientaation kontrollointi ripeillÀ raskailla ioneilla
Highly energetic ions have been previously used to modify the shape of metal nanoparticles embedded in an insulating matrix. In this work, we demonstrate that under suitable conditions, energetic ions can be used not only for shape modification but also for manipulation of nanorod orientation. This observation is made by imaging the same nanorod before and after swift heavy ion irradiation using a transmission electron microscope. Atomistic simulations reveal a complex mechanism of nanorod re-orientation by an incremental change in its shape from a rod to a spheroid and further back into a rod aligned with the beam.Highly energetic ions have been previously used to modify the shape of metal nanoparticles embedded in an insulating matrix. In this work, we demonstrate that under suitable conditions, energetic ions can be used not only for shape modification but also for manipulation of nanorod orientation. This observation is made by imaging the same nanorod before and after swift heavy ion irradiation using a transmission electron microscope. Atomistic simulations reveal a complex mechanism of nanorod re-orientation by an incremental change in its shape from a rod to a spheroid and further back into a rod aligned with the beam. Published under an exclusive license by AIP Publishing.Peer reviewe
Plasma etch characteristics of aluminum nitride mask layers grown by low-temperature plasma enhanced atomic layer deposition in SF6 based plasmas
The plasmaetch characteristics of aluminum nitride(AlN)deposited by low-temperature, 200â
°C, plasma enhanced atomic layer deposition (PEALD) was investigated for reactive ion etch (RIE) and inductively coupled plasma-reactive ion etch (ICP-RIE) systems using various mixtures of SF6 and O2 under different etch conditions. During RIE, the film exhibits good mask properties with etch rates below 10rânm/min. For ICP-RIE processes, the film exhibits exceptionally low etch rates in the subnanometer region with lower platen power. The AlN filmâs removal occurred through physical mechanisms; consequently, rf power and chamber pressure were the most significant parameters in PEALD AlN film removal because the film was inert to the SF+x and O+ chemistries. The etch experiments showed the film to be a resilient masking material. This makes it an attractive candidate for use as an etch mask in demanding SF6 based plasmaetch applications, such as through-wafer etching, or when oxide films are not suitable.Peer reviewe
Properties of Atomic Layer Deposited Nanolaminates of Zirconium and Cobalt Oxides
Five-layer crystalline thin film structures were formed, consisting of ZrO2 and Co3O4 alternately grown on Si(100) substrates by atomic layer deposition at 300 degrees C using ZrCl4 and Co(acac)(3) as the metal precursors and ozone as the oxygen precursor. The performance of the laminate films was dependent on the relative content of constituent oxide layers. The magnetization in these films was nonlinear, saturative, and with very weak coercive fields. Electrical measurements revealed the formation of significant polarization versus external field loops and implied some tendency toward memristive behavior. (C) The Author(s) 2018. Published by ECS.Peer reviewe
Ti Alloyed α -Ga 2 O 3: Route towards Wide Band Gap Engineering
The suitability of Ti as a band gap modifier for α-Ga2O3 was investigated, taking advantage of the isostructural α phases and high band gap difference between Ti2O3 and Ga2O3. Films of (Ti,Ga)2O3 were synthesized by atomic layer deposition on sapphire substrates, and characterized to determine how crystallinity and band gap vary with composition for this alloy. We report the deposition of high quality α-(TixGa1âx)2O3 films with x = 3.7%. For greater compositions the crystalline quality of the films degrades rapidly, where the corundum phase is maintained in films up to x = 5.3%, and films containing greater Ti fractions being amorphous. Over the range of achieved corundum phase films, that is 0% †x †5.3%, the band gap energy varies by âŒ270 meV. The ability to maintain a crystalline phase at low fractions of Ti, accompanied by a modification in band gap, shows promising prospects for band gap engineering and the development of wavelength specific solar-blind photodetectors based on α-Ga2O3
Recommended reading list of early publications on atomic layer deposition-Outcome of the "Virtual Project on the History of ALD"
Atomic layer deposition (ALD), a gas-phase thin film deposition technique based on repeated, self-terminating gas-solid reactions, has become the method of choice in semiconductor manufacturing and many other technological areas for depositing thin conformal inorganic material layers for various applications. ALD has been discovered and developed independently, at least twice, under different names: atomic layer epitaxy (ALE) and molecular layering. ALE, dating back to 1974 in Finland, has been commonly known as the origin of ALD, while work done since the 1960s in the Soviet Union under the name "molecular layering" (and sometimes other names) has remained much less known. The virtual project on the history of ALD (VPHA) is a volunteer-based effort with open participation, set up to make the early days of ALD more transparent. In VPHA, started in July 2013, the target is to list, read and comment on all early ALD academic and patent literature up to 1986. VPHA has resulted in two essays and several presentations at international conferences. This paper, based on a poster presentation at the 16th International Conference on Atomic Layer Deposition in Dublin, Ireland, 2016, presents a recommended reading list of early ALD publications, created collectively by the VPHA participants through voting. The list contains 22 publications from Finland, Japan, Soviet Union, United Kingdom, and United States. Up to now, a balanced overview regarding the early history of ALD has been missing; the current list is an attempt to remedy this deficiency. (C) 2016 Author(s).Peer reviewe
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