Breakdown Of Thin Films Research Articles

Breakdown field enhancement and energy storage performance in four-layered Aurivillius films

In dielectric capacitors, ferroelectric thin films with slim polarisation electric (P-E) hysteresis loops, which are mainly characterised by small residual polarisation (Pr) and large saturation polarisation (Ps) are expected to obtain high recoverable energy density (Ur) and efficiency (η). However, a lower breakdown in ferroelectric thin films usually impedes this result. Here, through the co-doping of La3+ and Pr3+ ions, a larger Ur of 54.27 J/cm3 and high η of 85.6% were obtained in four-layered Aurivillius phase ferroelectric thin films capacitors due to the enhanced breakdown electric field. The doped films annealed at relatively low temperatures showed similar energy storage properties compared with those of the prototype and higher energy storage efficiency compared with that of higher annealing films. In addition, the obtained thin film shows excellent energy storage properties in a wide frequency range, fatigue durability and good thermal stability. These results indicated that four-layered Aurivillius films are promising candidate materials for dielectric energy storage capacitors. The co-doping of double ions was an effective way to improve energy storage performance.

Urbach‐Energy‐Dictated Spatial Propagation of Electrons in Thermodynamically Tuned Amorphous Zirconia Thin Films

AbstractThermodynamically tuned zirconia thin films are fabricated for diverse Urbach energies in a homogeneous condensed system. In the analysis, the electrical breakdown of zirconia thin films is ascribed to the tunneling‐driven electron propagation involving virtual photons. An externally applied electric field is considered to expand the Urbach‐energy‐characterized energy distribution of sub‐bandgap states into their spatial distribution. In this expansion, the virtual‐photon energies activate the tunneling‐driven electron propagation through localized observer states. The integral of the virtual‐photon energies over the entire tunneling path is equal to the initial energy barrier.

Aqueous ionic effect on electrochemical breakdown of Si-dielectric\u2013electrolyte interface

The breakdown of thin dielectric films (SiO2, Si3N4, HfO2) immersed in aqueous electrolyte was investigated. The current and the kinetics of dielectric breakdown caused by large cathodic electric field applied across the dielectric layer reveal the electrochemical nature of dielectric materials. Electrolytes play a huge role in the established dielectric-electrolyte interface with respect to the overall electrical behavior of the system. Although aqueous cations are considered as spectator ions in most electrochemical systems, in dielectric interfaces the current–potential characteristics depend on the type of cation. Computer simulation based on density functional theory and molecular dynamics showed cations affect the dielectric strength. The responses of various dielectric films to solution components provide invaluable information for dielectric-incorporated electrochemical systems.

Barrier performance of ITO film on textured Si substrate

Indium tin oxide (ITO) film is the most widely used as front electrodes in solar cells with a copper metallization scheme. No work has focused on the barrier properties of the ITO layer on the textured silicon for solar cells. In this work, a thin indium tin oxide barrier layer and copper metal layer were deposited on textured (001) silicon by a sputtering. The stacks present Cu/ITO/Si. The structures of Cu/ITO/Si characterized by scanning transmission electron microscope, energy-dispersive X-ray spectrometer, and powder X-ray diffraction. The results show that the stacks of Cu/ITO/Si can be preserved up to 600 °C. The 35-nm thickness ITO layer was found to be a diffusion barrier against Cu up to 600 °C. The copper thin films were agglomerated and formed the particle at a temperature of 700 °C. The failure of Cu/ITO/Si can be attributed to agglomerate copper thin films and breakdown of ITO thin films at a temperature of 700 °C.

The universal character of the breakdown of condensed media by powerful terahertz radiation and the Abbe criterion

This paper analyzes new experimental results on the surface breakdown of semiconductors and thin metallic films by ultrashort pulses of plane-polarized terahertz radiation. It shows that the character of the observed breakdown is satisfactorily explained by the universal polariton model, tested with ultrashort pulses of visible and near-IR radiation interacting with condensed media. By using a nonlinear mathematical model of the formation of the spatial periods of a nanograting that are multiples of the wavelength of the exciting radiation, it is shown that the periods of the gratings thus formed are substantially shorter than the linear diffraction limit in the optical and terahertz regions. It is demonstrated that the diffraction limit can be overcome in nonlinear processes by which interference nanogratings are formed with normal and anomalous orientations.

Data-Driven Modeling of Dielectric Breakdown Phenomena in Polymers

Polymers are widely used as dielectrics in devices ranging from capacitors to multi-layered IC’s and as insulation for high voltage cables. In these applications, the dielectric breakdown strength is a critical parameter affecting device performance [1]. In this work, we study the dielectric breakdown properties of common polymers using machine learning. The complex nature of the dielectric breakdown process makes it analytically intractable for real systems and thus ideal for application of machine learning. The input to the machine learning model consists of material property values and the model outputs dielectric breakdown. For our training data, dielectric breakdown of polymer thin films is experimentally measured using small area breakdown measurements [2] at multiple temperatures ranging from -100 °C to 100 °C. The input to our model are property data that are known to influence dielectric breakdown. Selecting a subset of our original feature space using variable selection algorithms, we train a machine learning model using gaussian process regression. We test our model on unseen experimental data and find that it predicts dielectric breakdown of unseen polymers accurate to the experimental error of measurement. In addition we find that the underlying physics of the temperature dependence of dielectric breakdown is captured well in the training domain. Our model can be used to systematically search polymer spaces to accelerate discovery of high breakdown strength polymers.

Novel BiAlO3 dielectric thin films with high energy density

Annealing temperature is a key element affecting the electrical properties and microstructure of dielectric thin films. In this case, BiAlO3 (BA) thin films were spin-coated on the Pt/Ti/SiO2/Si(100) substrates by sol-gel method and annealed at the temperature ranging from 450 °C to 550 °C. Then the influences of annealing temperatures on the microstructure, dielectric breakdown, and ferroelectric polarization of BiAlO3 thin films were studied. A optimal recoverable energy storage density (Wreco) of 31.1 J/cm3 and efficiency of 82.2% were achieved for the BA thin films annealed at 500 °C due to the ultrahigh dielectric breakdown strength (BDS) of 3535.7 kV/cm. This study offers a new paradigm for developing high-performance lead-free dielectric materials, which can largely extend the energy storage application of Bi-base perovskite materials.

Push-Button Method To Create Nanopores Using a Tesla-Coil Lighter.

Controlled dielectric breakdown (CDB) of silicon nitride thin films immersed in electrolyte solution has been used to fabricate single nanofluidic channels with ∼10 nm and smaller diameters, nanopores, useful in single-molecule sensing and ionic circuit construction. A hand-held Tesla-coil lighter was used to form nanofluidic ionic conductors through a ∼10 nm thick silicon nitride membrane. Modifications to the conventional approach were required by the low-overhead Tesla-coil-assisted method (TCAM): increased circuit resistance by including water in place of electrolyte and discrete rather than continuous voltage applications. The resulting ionic conductance could be tuned with the number of voltage applications. TCAM and conventional CDB produced nanopores with different conductance versus pH curves, suggesting different surface chemistry. Nevertheless, sensing experiments using the canonical test molecule, λ-DNA, produced signals comparable to translocation results through solid-state nanopores fabricated by other methods. Thus, the TCAM method offers flexibility in fabrication and in the properties and function of the nanoscale ionic conductors that it can generate.

Experimental investigations into triplex hybrid process of GA-RDECDM during subtractive processing of MMC’s

ABSTRACTThe use of Al-6063 SiCp metal matrix composites (MMCs) in electronic packaging applications, heat sinks for printed circuit boards and for microwave housings necessitates certain degree of machining operations to meet the specifications of the product. The various conventional and non-conventional machining processes had been used to machine the MMCs. But all such processes have their limitations in providing the desired outcomes. Therefore, the present research endeavor, a new process variant of ECDM for the machining of Al-6063 SiCp MMCs. The developed grinding assisted rotary disk electrochemical discharge machining (GA-RDECDM) process integrates the concept of triplex hybridization. In GA-RDECDM, an abrasive coated rotary disk was used as a tool electrode. The abrasive coated disk provides micro gaps between the tool electrode and work material surface and thereby it results in thin and stable gas film formation. The breakdown of thin and stable gas films produce high frequency, low intensity discharges and consequently improves the machining performance. The additional abrasion action imparted by rotating disk ensures the continuation of ECDM process. The influence of various process parameters including applied voltage, pulse on time, electrolyte concentration and the disk rotation rate on width over cut (WOC) and depth were experimentally investigated. Multi criteria optimization using desirability approach predicts the parametric combination of applied voltage of 99V, pulse on time of 3 ms, electrolyte concentration of 17%wt./vol. and disk rotation rate of 30 rpm as the optimum setting for fabrication of slits on the MMCs. The underlying process mechanism is also investigated and presented with appropriate illustrations. The major contribution of the present research work is the development of a novel method for the fabrication of the slits on MMCs.

Dielectric breakdown of alumina thin films produced by pulsed direct current magnetron sputtering

Alumina films (~2 μm thick) were deposited with a mixed Cu/Al interlayer onto copper. Direct current (DC)/Pulsed DC (PDC) magnetron sputtering techniques were independently compared for reactive alumina sputtering. In DC sputtered films, elemental aluminium of 9.2 at.% and nano-crystallites were present within the x-ray amorphous matrix, resulting from target arcing. Defects lead to premature dielectric breakdown/increased current leakage. PDC sputtering improved film quality by removing crystallites, metallic clusters and through thickness cracking. Time dependent dielectric breakdown (TDDB) measurements were carried out using conductive atomic force microscopy identified an improvement in dielectric strength (166 to 310 V μm−1) when switching from DC to PDC deposition power. TDDB suggested that at high applied field the dominant pre-breakdown conduction mechanism was Fowler-Nordheim tunnelling in DC films. Tensile pull-off adhesion ranged from 56 to 72 MPa and was highest following incorporation of an Cu/Al blended interfacial layer. Scratch testing indicated various cracking/buckling failures.

An X-ray and Neutron Reflectometry Study of Iron Corrosion in Seawater

The corrosive breakdown of thin iron films supported on silicon substrates under a number of conditions is presented-in particular to understand better how iron, and hence ferritic steel, behaves in a salty water environment. A combination of X-ray and neutron reflectometry was used to monitor the structures of both metal and oxide surface layers and also organic corrosion inhibitors adsorbed at the iron/aqueous interface. A range of behavior in seawater was observed, including complete dissolution and void formation under the metal surface. Importantly, two simple treatments-UV/ozone or soaking in ultrapure water-were found to significantly protect the iron surface for considerable lengths of time, although evidence of pitting corrosion began after around 10 days. The underlying causes of the efficacies of these treatments were further investigated using X-ray photoelectron spectroscopy. In addition, three potential corrosion inhibitors were investigated: (i) dodecyltrimethylammonium bromide (DTAB) demonstrated no ability to protect the surface; (ii) sodium dodecyl sulfate (SDS) appeared to accelerate corrosion; and (iii) bis(2-ethylhexyl)phosphate showed an impressive level of protection (the neutron reflectometry results indicated a thick diffuse layer of surfactant of 23% surface coverage). These findings have been interpreted in terms of preferential inhibitor adsorption at cathodic and anodic surface sites (depending on the nature of the inhibitor).

On performance evaluation of textured tools during micro-channeling with ECDM

Electrochemical discharge machining (ECDM) is an emerging technique for machining of micro-channels on non-conductive materials. It utilizes a combination of chemical as well as thermal energies to machine the materials. The configuration of tool electrode plays important role to channelize these energies from tool electrode to work material. Thus, the appropriate selection of tool electrode configuration is essential to effectively utilize the energies during ECDM for achieving machining accuracy. The present investigation reports on textured tools for machining of micro-channels on borosilicate glass with ECDM. The underlying process mechanism is investigated. Textured tools provides micro gaps between the tool electrode and the workpiece surface and results in thin and stable gas films. The breakdown of thin and stable gas films produces high frequency low intensity discharges and consequently improves the machining performance. The textured tools in comparison with smooth surfaced tools exhibits improvements in material removal rate (MRR) by 19.27% and depth by 64.81%. Also the width overcut (WOC) and surface roughness were reduced by 122.26% and 26.96%, respectively. The flexibility to develop textured as well as smooth micro-channel surfaces by textured tools provides wider scope for fabrication of various micro fluidic devices. The effect of ECDM process parameters (voltage, pulse on-time, pulse off-time, feed rate and electrolyte concentration) with the use of textured tools was investigated. Multi criteria optimization using desirability approach predicted the parametric combination of applied voltage of 59 V, pulse on-time of 3 ms, pulse off-time of 3 ms, feed rate of 12 m m/min. and electrolyte concentration of 21%wt./vol., the optimum setting for micro-channelling by ECDM using textured tools.

Mechanical stress effects on electrical breakdown of freestanding GaN thin films

Gallium Nitride (GaN) devices are intended to operate at high temperature and mechanical stress conditions, rendering reliability a major concern. To investigate the effects of temperature and stress on electrical breakdown they were applied individually and simultaneously, on free standing epitaxially grown GaN specimens after release from the growth substrate. Both temperature and mechanical stress were seen to degrade the material by decreasing the breakdown voltage. Up to 60% decrease was observed at around 870MPa. It is hypothesized that stress-generated defects climb to the free surfaces, creating localized leakage current instability or 'ringing' effects. This study also captures the synergy of temperature and stress, which can be translated to breakdown of buffer layers in GaN devices or in designing harsh environment sensors.

Extrinsic time-dependent dielectric breakdown of low-k organosilicate thin films from vacuum-ultraviolet irradiation

In this work, the effect of vacuum ultraviolet (VUV) photon irradiation on the time-dependent dielectric breakdown (TDDB) of low-k organosilicate thin films was investigated, with particular emphasis on extrinsic TDDB (includes Cu migration effects). State-of-the-art low-k a-SiOC:H thin films were utilized because of their relevance as both an interlayer dielectric and as a candidate Cu capping-layer material. Synchrotron radiation was used to mimic VUV photon irradiation from processing plasmas without the presence of charged particles. TDDB characteristic lifetimes of the low-k a-SiOC:H dielectrics, before and after VUV photon exposure, were measured based on a Ti/a-SiOC:H/Cu metal-insulator-metal structure. The deterioration of extrinsic TDDB was observed in the film after exposure to VUV photons with 9 eV energy. The most notable degradation of the dielectric characteristic lifetime was found when the Cu electrode was used as an anode in the sample after 9.0 eV VUV photon exposure (photon fluence is 4.0 × 1015 photons/cm2). This is believed to be related to the Cu+ ions created by a VUV photon-assisted reaction. In the presence of an electric field, these Cu ions drift into the low-k dielectric and deteriorate TDDB performance.

Effect of NiO crystallinity on forming characteristics in Pt/NiO/Pt cells as resistive switching memories

Resistive switching (RS) in metal/oxide/metal stack structures plays a key role in resistive RAM. The formation and rupture of conductive filaments have been widely accepted as an origin of RS mechanism especially in binary transition metal oxides. Forming exhibits some analogies with a dielectric breakdown of SiO2 thin films. In this study, Time-Dependent Forming (TDF) characteristics of Pt/NiO/Pt stack structures have been investigated. The results revealed that the formation of conductive filaments at the forming process by applying constant voltage followed a weakest-link theory and that the weakest spots were almost randomly distributed in NiO thin films according to the Poisson statistics. Furthermore, the distribution of TDF characteristics depends on NiO crystallinity. A small variation of initial resistance tends to result in a large variation of time to forming and vice versa.

Endurance-write-speed tradeoffs in nonvolatile memories

We derive phenomenological model for endurance-write time switching tradeoff for nonvolatile memories with thermally activated switching mechanisms. The model predicts linear to cubic dependence of endurance on write time for metal oxide memristors and flash memories, which is partially supported by experimental data for the breakdown of metal-oxide thin films.

Comparative analysis of breakdown mechanism in thin SiO2 oxide films in metal–oxide–semiconductor structures under the action of heavy charged particles and a pulsed voltage

Regularities in the breakdown of thin SiO2 oxide films in metal–oxide–semiconductors structures of power field-effect transistors under the action of single heavy charged particles and a pulsed voltage are studied experimentally. Using a phenomenological approach, we carry out comparative analysis of physical mechanisms and energy criteria of the SiO2 breakdown in extreme conditions of excitation of the electron subsystem in the subpicosecond time range.

Breakdown and Protection of ALD Moisture Barrier Thin Films.

The water vapor barrier properties of low-temperature atomic layer deposited (ALD) AlOx thin-films are observed to be unstable if exposed directly to high or even ambient relative humidities. Upon exposure to humid atmospheres, their apparent barrier breaks down and their water vapor transmission rates (WVTR), measured by electrical calcium tests, deteriorate by several orders of magnitude. These changes are accompanied by surface roughening beyond the original thickness, observed by atomic force microscopy. X-ray reflectivity investigations show a strong decrease in density caused by only 5 min storage in a 38 °C, 90% relative humidity climate. We show that barrier stabilities required for device applications can be achieved by protection layers which prevent the direct contact of water condensing on the surface, i.e., the sensitive ALD barrier. Nine different protection layers of either ALD materials or polymers are tested on the barriers. Although ALD materials prove to be ineffective, applied polymers seem to provide good protection independent of thickness, surface free energy, and deposition technique. A glued-on PET foil stands out as a low-cost, easily processed, and especially stable solution. This way, 20 nm single layer ALD barriers for organic electronics are measured. They yield reliable WVTRs down to 2×10(-5) g(H2O) m(-2) day(-1) at 38 °C and 90% relative humidity, highlighting the great potential of ALD encapsulation.

Temperature dependant dielectric breakdown of sputter-deposited AlN thin films using a time-zero approach

In MEMS (micro electromechanical system) devices, piezoelectric aluminum nitride (AlN) thin films are commonly used as functional material for sensing and actuating purposes. Additionally, AlN features excellent dielectric properties as well as a high chemical and thermal stability, making it also a good choice for passivation purposes for microelectronic devices. With those aspects and current trends towards minimization in mind, the dielectric reliability of thin AlN films is of utmost importance for the realization of advanced device concepts. In this study, we present results on the transversal dielectric strength of 100 nm AlN thin films deposited by dc magnetron sputtering. The dielectric strength is measured using a time-zero approach, using a fast voltage ramp to stress the film up to the point of breakdown. The measurements are performed at different device temperatures. In order to achieve statistical significance, at least 12 measurements are performed for each environment parameter set and the results are analyzed using the Weibull approach. Basically, lower breakdown fields are observed with increasing temperatures up to 300 °C with a characteristic breakdown field strength E0 following the relationship $$\sqrt {E_{0} } \propto T$$E0źT as reported in literature for similar measurements performed at silicon nitride thin films. From the intersection of this linear behavior, the Poole---Frenkel (PF) barrier height źB is determined to 0.54 eV, which is reasonable for AlN thin films. The slope of this relation is similar to values reported for silicon nitride thin films. This allows an estimation of the breakdown field at higher temperatures by extrapolation. Leakage current measurements show a dominant PF type conduction mechanism, verifying the applicability of $$\sqrt {E_{0} } \propto T$$E0źT. No breakdown occurs in negative field direction, which is attributed to the metal---insulator---semiconductor configuration of the sample and hence, the presence of a depletion layer forming in the n-doped silicon and dominating the leakage current behavior.

Optical breakdown of multilayer thin-films induced by ultrashort pulses at MHz repetition rates

Multilayer coatings composed of TiO(2), Ta(2)O(5), HfO(2), or Al(2)O(3) as high-index materials and SiO(2) as low-index material were investigated for laser-induced damage using 1 ps, 5 µJ pulses generated by a mode-locked Yb:YAG thin-disk oscillator operating at a wavelength of 1030 nm and repetition rate of 11.5 MHz. Previously reported linear band gap dependence of damage threshold at kHz repetition rates was confirmed also for the MHz regime. Additionally, we studied the effect of electric field distribution inside of the layer stack. We did not observe any significant influence of thermal effects on the laser-induced damage threshold in this regime.