TiN Layer Thickness Research Articles

Towards a CMOS compatible refractive index sensor: cointegration of TiN nanohole arrays and Ge photodetectors in a 200 mm wafer silicon technology

In this work, we present the monolithic integration of a TiN nanohole array and a Ge photodetector towards a CMOS compatible fabrication of a refractive index sensor in a 200 mm wafer silicon technology. We developed a technology process that enables fabrication with high yields of around 90%. Ge photodetectors with a Ge layer thickness of 450 nm and an area of 1600 µm2 (40 µm x 40 µm) show dark current densities of around 129 mA/cm2 and responsivities of 0.114 A/W measured by top illumination (TE polarization; λ = 1310 nm; angle of incidence = 14 °) at a reverse bias of 1 V. Nanohole arrays were structured in a 150 nm thick TiN layer. They were integrated into the back end of line and placed spatially close to the Ge photodetectors. After the metallization, passivation, and pad opening, the nanohole arrays were released with the help of an amorphous silicon stop layer. A significant impact of the TiN nanohole arrays on the optical behavior of the photodetector could be proven on the wafer level. Photocurrent measurements by top illumination confirm a strong dependence of optical properties on the polarization of the incident light and the nanohole array design. We demonstrate very stable photocurrents on the wafer level with a standard deviation of σ < 6%.

Increasing the wear resistance of hip prostheses components using micro-nanostructured thin layers

Evaluation of micro-nanostructured thin layers applicability for increasing the lifetime of rehabilitation systems, mainly hip prostheses, is the aim of the present research. This because, the final objective of the complete project is to improve the quality of human prostheses using micro-nanostructured thin layers. In order to realize these researches, 0.5, 1, and 1.5 µm thick thin layers of TiN and TiO2, were deposited on substrates made of materials currently used for hip prostheses – M30NW steel and CoCr – using physical deposition methods, respectively Cathodic Arc (CA), Direct Current (DC) sputtering and High-Power Impulse Magnetron Sputtering (HiPIMS). After tribological and nanoindentation tests, the 1.5 μm thick TiN and TiO2 thin layers deposited on the steel and CoCr substrates using the DC sputtering method presented superior mechanical properties. Functional characterization of a total hip prosthesis, that have had components coated with these thin layers presented an increased resistance to fatigue wear. After comparative analysis, the main conclusion of the realized researches was that TiN layers with a thickness of 1.5 μm have an increased resistance to fatigue wear in comparison with TiO2 layers, when both are deposited by DC sputtering on M30NW steel and CoCr substrates. It was observed that 1.5 μm thick TiN layers ensures a prolongation by 15% of the lifetime of femoral heads compared to those uncoated.

TiN-Au/HfO2 -Au Multilayer Thin Films with Tunable Hyperbolic Optical Response.

Hyperbolic metamaterials (HMM) possess significant anisotropic physical properties and tunability and thus find many applications in integrated photonic devices. HMMs consisting of metal and dielectric phases in either multilayer or vertically aligned nanocomposites (VAN) form are demonstrated with different hyperbolic properties. Herein, self-assembled HfO2 -Au/TiN-Au multilayer thin films, combining both the multilayer and VAN designs, are demonstrated. Specifically, Au nanopillars embedded in HfO2 and TiN layers forming the alternative layers of HfO2 -Au VAN and TiN-Au VAN. The HfO2 and TiN layer thickness is carefully controlled by varying laser pulses during pulsed laser deposition (PLD). Interestingly, tunable anisotropic physical properties can be achieved by adjusting the bi-layer thickness and the number of the bi-layers. Type II optical hyperbolic dispersion can be obtained from high layer thickness structure (e.g., 20 nm), while it can be transformed into Type I optical hyperbolic dispersion by reducing the thickness to a proper value (e.g., 4 nm). This new nanoscale hybrid metamaterial structure with the three-phase VAN design shows great potential for tailorable optical components in future integrated devices.

Thickness regulation of the mechanical properties and failure control of Ti/TiN and Ti(N)/TiN bilayer stacks

Magnetron sputtering and hot-wire plasma-enhanced nitriding were combined to prepare bilayers of Ti/TiN or Ti(N)/TiN with different thickness ratio deposited on Ti6Al4V (TC4) alloy substrates to form stacks of four bilayers. The structural and mechanical properties and adhesion of the films to the substrate were evaluated. The results showed that the surface morphology of the stacks became smoother as the Ti, Ti(N)/TiN thickness ratios were decreased from 1:2 to 1:8 and 1:17 by reducing the proportion the Ti or Ti(N) layer thickness while increasing the proportion of the TiN layer thickness in the four-bilayer stacks. The primary preferred orientation of Ti (002) and TiN (111) were observed in the multilayer films, while Ti (002) shifted to a lower angle in Ti(N)/TiN, which proved the solid solution of N atoms into the Ti lattices following nitridation of the Ti bottom layers. The hardness, elastic modulus, and wear resistance of the four bilayer stacks also increased with the nitridation of the bottom Ti layer. The mechanical properties of the Ti(N)/TiN bilayer stacks were better than those of the Ti/TiN films while the difference between the samples reduced as the relative proportion of the Ti or Ti(N) layers was decreased. The adhesion between the multilayer stacks and the TC4 substrates, evaluated by both scratch and Rockwell tests, was improved as the thickness ratios of the Ti or Ti(N) bottom layers decreased to 1:8 and 1:17. The adhesion between the films and the substrates were improved by reducing the proportion of soft Ti or Ti(N) and increasing the elastic modulus of the soft layer through nitriding to reduce the modulus difference between the bilayer stacks and TC4 substrate, as well as the Ti or Ti(N) layer and the TiN layer.

Cross-interface growth mechanism of nanotwins in extremely high stacking-fault energy ceramic layer

Twins have been proven to greatly enhance the hardness, toughness, thermal stability, and wear resistance of materials. However, the formation of twins in transition nitride ceramics is exceptionally difficult due to their prohibitively high stacking-fault energy. Consequently, reports on nanotwinned ceramic films have been limited in scope. In this study, we utilize the template effect of multilayer structures to induce the growth of nanotwins within the high stacking-fault energy TiN and AlN layers. Theoretical analysis reveals that the growth of nanotwins across the interface is facilitated by the template effect and large internal stress. The former fosters the epitaxial growth of nanotwinned two-sided structures into the TiN and AlN layers. Simultaneously, the pronounced internal stress engenders substantial lateral stress in the TiN and AlN layers immediately above the underlying nanotwin region, ultimately leading to the formation of nanotwins. In addition, due to the differences in lattice constants and crystal structures of TiN and AlN, the maximum thickness of TiN layer that can sustaining stable growth of nanotwins is about 10 nm, whereas for AlN layer is just about 1.5 nm. This study proposes a promising approach to introduce twins in ceramic films with exceedingly high stacking-fault energies and enable advancements in the toughening of ceramic films.

Oxidation mechanism of sputter deposited model SiNx/TiN/SiNx coatings

TiSiN coatings are of high interest for the cutting industry, since they not only offer excellent mechanical properties, but also exhibit exceptional oxidation resistance. Although up to date several studies have been conducted on evaluating the oxidation resistance of nanocomposite TiSiN coatings, the influence of the shielding effect of the amorphous SiNx phase on the nanocrystalline TiN phase during oxidation has not yet been illuminated in detail. Therefore, the aim of this work is to provide insight into this shielding effect by using a three-layer SiNx/TiN/SiNx model system. Three different SiNx layer thicknesses of 150, 300 and 800 nm were investigated, while the TiN layer thickness was with 900 nm identical for all coatings. The results revealed that the amorphous SiNx efficiently shields TiN against oxidation up to temperatures exceeding 800 °C, whereby the exact oxidation onset temperature increased with increasing SiNx layer thickness. After reaching a critical temperature, both the TiN and amorphous SiNx phase were found to exhibit a porous structure, leading to oxidation of the TiN layer and growth of coarsened TiO2 grains, which eventually break the SiNx top layer. Furthermore, amorphous SiNx was shown to be significantly more resistant to oxidation compared to crystalline TiN, being still mainly non-oxidized after oxidation at 1200 °C for 30 min. The present study allows to gain insight into the underlying mechanisms of the shielding effect of amorphous SiNx on TiN using a model coating system, thus providing a deeper understanding of the oxidation behavior of TiSiN nanocomposite coatings.

Comparison Study of PVD Coatings: TiN/AlTiN, TiN and TiAlSiN Used in Wood Machining.

In this paper, we analyze the possibilities of the protection of tools for wood machining with PVD (Physical Vapor Deposition) hard coatings. The nanolayered TiN/AlTiN coating, nanocomposite TiAlSiN coatings, and single layer TiN coating were analyzed in order to use them for protection of tools for wood machining. Both nanostructured coatings were deposited in an industrial magnetron sputtering system on the cutting blades made of sintered carbide WC-Co, while TiN single layer coating was deposited by evaporation using thermionic arc. In the case of TiN/AlTiN nanolayer coatings the thickness of the individual TiN and AlTiN layer was in the 5–10 nm range, depending on the substrate vertical position. The microstructure and chemical composition of coatings were studied by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) method. Additionally, in the case of the TiN/AlTiN coating, which was characterized by the best durability characteristics, the transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) methods were applied. The coatings adhesion to the substrate was analyzed by scratch test method combined with optical microscopy. Nano-hardness and durability tests were performed with uncoated and coated blades using chipboard. The best results durability characteristics were observed for TiN/AlTiN nanolayered coating. Performance tests of knives protected with TiN and TiAlSiN hard coatings did not show significantly better results compared to uncoated ones.

Tribological Behavior of Electrical Connector Coatings Under Reciprocating Motion

Abstract With the rapid growth in the use of electronics, more studies are focusing on the tribological performance of electrical connectors. The most common electroplating coating materials are tin and copper. One major issue is when fretting corrosion produces metal oxides, which are likely to increase the electrical resistance at the contact interface. This research aims to reduce metal oxidation of electrical connectors by studying the tribological performance of various thicknesses of tin and copper layers with a designated electrical circuit to be used with a reciprocating wear test. This research considers the effect of tin and copper layer thickness, including the lack of a tin layer, on the tribological behavior. Among coatings tested, a thin coating of copper with no tin resulted in the least wear. A thicker coating of copper significantly increased the wear due to the high roughness of the sample with a thick copper coating. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) results indicated that adhesive wear occurred during sliding. Adhered particles led to two-body abrasive wear and when the adhered particles break away three-body abrasive wear is produced.

(Invited, Digital Presentation) Approach to Neuromorphic Computing with Ferroelectric Schottky Barrier FETs

Neuromorphic computing inspired by neural network systems of the human brain enables energy efficient computing as a solution of the von Neumann bottleneck. A neural network consists of thousands or even millions of neurons which communicate with each other through connected synapses. Synapses can memorize and process the information simultaneously. The plasticity of a synapse to strengthen or weaken its activity over time make it be capable of learning and computing. Thus, artificial synapses which can emulate functionalities and the plasticity of bio-synapses form the backbone of a neuromorphic computing system.Non-volatile memories with two-terminals, like resistive random-access memory (ReRAM), phase change memory (PCM), are attractive candidates for artificial synapses. However, signal processing and learning cannot be performed simultaneously in these two-terminal synapses. FeFET, similar to a MOSFET structure using CMOS compatible HfO2 based ferroelectrics as gate oxide forms three-terminal synapses offering high endurance, good performance and high energy efficiency. In contrast to two-terminal devices, three terminal FeFET based synapses can perform processing and learning at the same time. In order to maintain the ferroelectric properties of an HfO2 based ferroelectric film, high temperature annealing should be avoided after the ferroelectric layer deposition. In this paper, we present ferroelectric NiSi2 source/drain Schottky barrier (SB) MOSFET (FE-SBFET) structure (Fig.1a), which requires neither ion implantation nor thermal activation of source/drain contacts at high temperatures.FE-SBFETs were fabricated on SOI substrates with a boron-doped (1016 B/cm-3), 55 nm thick top Si layer and a 145 nm thick buried oxide (BOX) layer. Very thin (9 nm) single crystalline NiSi2 layers which offer superior properties of uniform and stable SB contacts on Si are used at source/drain regions. A gate stack consisting of 10 nm thick Hf0.5Zr0.5O2 (HZO) layer and a 40 nm thick TiN layer are deposited by ALD and sputtering, respectively. A rapid thermal annealing at 500 °C is performed to crystallize the HZO into a ferroelectric phase before the gate patterning. The fabricated device has a channel length of 10 µm and a gate width of 10 µm. The overlap between the top gate and NiSi2 is 6 µm along the channel and 10 µm wide on each side. The ferroelectric polarization modulates both the SB at the source/drain contacts as well as the potential in the channel, thus changing the carrier injection through the SB. The Id-Vg transfer characteristics of a p-type FE-SBFET shows a clockwise hysteresis which is caused by the ferroelectric polarization switch.The excitatory post-synaptic current (EPSC), one of the typical short-term synaptic plasticity features for biologic synapses, is characterized by measuring the transient drain currents for a voltage pulse on the gate of a FE-SBFET (Fig.1b). The amplitude of the pulse VAM changes from -0.2 to -1.2 V with a fixed pulse width tpw=1 μs. We found that the EPSC peak value increases linearly with VAM. It shows a very low energy/spike consumption of 2fJ/spike at VAM=-0.2 V, demonstrating a very high energy efficiency. From the EPSC measurements with repeated gate voltage pulses paired-pulse facilitation/depression (PPF/PPD) are characterized showing an exponential decay, similar to biological synapses.The long-term synaptic plasticity of FE-SBFET synapses is characterized by a series repeated identical or non-identical pulses. The later can improve the long-term potentiation/depression (LTP/LTD) symmetry and linearity. The measurements show a large Gmax/Gmin ratio, very high endurance and small cycle-to-cycle (CTC) variation (1.06%) due to the perfect contact of NiSi2 (Fig.1c). The biological neuron-like spike-timing-dependent plasticity (STDP) is characterized for the FE-SBFET synapse. The results show an asymmetric anti-Hebbian STDP, which is one of the biological STDP functionalities (Fig.1d).In conclusion, the fabricated FE-SBFET synapse exhibits multiple synaptic functions with high endurance and small variations. The ultra-low energy/spike consumption indicates a high potential for low power neuromorphic computing applications. Acknowledgement: This work was supported by the Federal Ministry of Education and Research (BMBF, Germany) in the project NEUROTEC (16ME0398K). Figure 1

Suppressing photoluminescence and enhancing light absorption of TiO2 via using TiO2/TiN/TiO2 plasmonic multilayers for better solar harvesting

In this work, TiO2/TiN/TiO2 multilayer nanostructured films are prepared for coupling the plasmonic characteristics of TiN with the semiconducting characteristics of TiO2. X-ray examinations revealed the existence of mixed tetragonal crystalline phases of anatase and rutile TiO2. Small and uniformly distributed grains with grain sizes ranged from 5 to 9 nm were observed from scanning electron microscopy investigations. The electrical conductivity of the nanostructured multilayer films increased monotonically with increasing TiN layer thickness. Five-phase Si(substrate)/TiO2/TiN/TiO2/air model was employed to fit the simulated data to the experimental spectroscopic ellipsometer spectra. The refractive index and the real part of the dielectric constant were generally decreased with increasing TiN thickness. The absorption was enhanced over the wavelengths from 650 to 1350 nm, in which traditional silicon solar cells display a weak achievement, with increasing TiN layer thickness. The optical band gap values were decreased from 3.32 eV to 3.01 eV with increasing TiN layer thickness from 2.9 nm to 32.1 nm. Severe quenching in the photoluminescence intensity was observed with increasing TiN layer thickness. This study showed TiO2/TiN/TiO2 multilayer films with enhanced plasmonic characteristics, enhanced absorbance and quenched photoluminescence which can be used to enhance their potential applications in solar energy harvesting.

Investigation of Interfacial Microstructures of TiN/AlN Multilayers by Neutron Reflectometry

Three alternate TiN/AlN nanostructured multilayers with the TiN layer thicknesses of 60, 70, and 120 Å and the AlN layer thickness of 10 Å were fabricated using dc reactive magnetron sputtering. Microstructural characterizations of the three nano-scale films were performed using nonpolarized specular neutron reflectometry. The results showed that the three TiN/AlN multilayer thin films were typical superlattice films and the thicknesses of the TiN layer and AlN layer in the multilayers were consistent with the design thickness nearly. The interface roughness was asymmetric in all the samples. The interface of AlN growing on TiN was much sharper than that of TiN growing on AlN and the latter was the diffusion interface in the TiN/AlN multilayer films.

Effect of TiN diffusion barrier layer on residual stress and carrier transport in flexible CZTSSe solar cells

The major drawback of flexible Cu2ZnSn(S,Se)4 (CZTSSe) solar cells is the inevitable residual stress in CZTSSe that considerably limits the efficiency and flexibility of these cells. Hence, in this work, TiN layers with varying thicknesses were sputtered between flexible Ti substrates and back contact Mo layers as diffusion barriers. The TiN barrier layer relieved residual stress, facilitated grain growth, and decreased the porosity of CZTSSe, thereby effectively suppressing the formation of carrier recombination paths and improving the mechanical strength of CZTSSe. Meanwhile, the band alignment of the CZTSSe/CdS heterojunction could be significantly tailored, leading to an improved ‘‘cliff-like’’ conduction band offset from −0.49 eV to −0.33 eV. Under the optimized TiN layer thickness of 50 nm, the power conversion efficiency of the fabricated flexible CZTSSe solar cell increased considerably from 3.43% to 4.85% along with high bending stability. Therefore, introducing the TiN diffusion barrier into traditional flexible CZTSSe solar cells improves the efficiency and flexibility of these devices. Moreover, this method could be a promising pathway for the large-scale production of smart, flexible, and portable electronic devices.

Study on Influence of Tin Plating Layer of Solder Strip on Electrical Properties of Photovoltaic Modules

With the continuous development of social economy, the cost reduction and efficiency increase of enterprises are very important for the development of enterprises. Starting from the packaging materials of photovoltaic modules, this paper mainly studies the influence of welding ribbon with different tin layer thicknesses on the performance of photovoltaic modules, and compares the resistivity of welding ribbon with different thickness of tin layers. The experimental results show that with the reduction of the thickness of the tin-plated layer on the non-soldering surface of the welding ribbon, the resistivity of the welding ribbon decreases, and the output power of the photovoltaic module is effectively improved.

Long-life lithium-sulfur batteries with high areal capacity based on coaxial CNTs@TiN-TiO2 sponge

Rational design of heterostructures opens up new opportunities as an ideal catalyst system for lithium polysulfides conversion in lithium-sulfur battery. However, its traditional fabrication process is complex, which makes it difficult to reasonably control the content and distribution of each component. In this work, to rationally design the heterostructure, the atomic layer deposition is utilized to hybridize the TiO2-TiN heterostructure with the three-dimensional carbon nanotube sponge. Through optimizing the deposited thickness of TiO2 and TiN layers and adopting the annealing post-treatment, the derived coaxial sponge with uniform TiN-TiO2 heterostructure exhibits the best catalytic ability. The corresponding lithium-sulfur battery shows enhanced electrochemical performance with high specific capacity of 1289 mAh g−1 at 1 C and capacity retention of 85% after 500 cycles at 2 C. Furthermore, benefiting from the highly porous structure and interconnected conductive pathways from the sponge, its areal capacity reaches up to 21.5 mAh cm−2.

Improving corrosion resistance of 3D printed Ti-6Al-4V by TiN coating

TiN thin films were deposited on biomaterial 3D printed Ti-6Al-4V substrates using two methods including direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS). The coating times were compared between 5 min and 25 min. HiPIMS was developed based on DCMS by increasing degree of ionization in plasma and power densities in the order of kWcm-2 compared to Wcm-2 of DCMS. The film characteristics and mechanical properties were investigated by glancing incident x-ray diffractometer (GIXRD), field emission scanning electron microscope (FE-SEM), and atomic force microscope (AFM). Electrochemical behavior was analyzed by electrochemical impedance spectroscopy (EIS) in 1 M NaCl solution. The results showed that TiN films deposited by HiPIMS exhibited an equiaxed structure while those from DCMS had a columnar structure. As a consequence, corrosion resistance of HiPIMS films was better than the DCMS films. Furthermore, increasing coating time resulted in thicker TiN layer and therefore, promoted higher corrosion resistance.

Interfacial and mechanical characteristics of TiN/Al composites under nanoindentation

This paper investigates the influence of the surface orientation of TiN and Al layers, as well as TiN layer thickness on the deformation behavior and mechanical characteristic of TiN/Al bilayer composites under the nanoindentation process through molecular dynamics (MD) simulation. The result shows that the TiN(111)/Al(111) workpiece with Ti-face has the greatest loading force and hardness, indicating that the strength of this specimen is improved better than other surface orientations, and the increase in TiN layer thickness leads to increase the loading force and hardness. However, defects such as dislocation and phase transformation appear also more in the TiN(111)/Al(111) workpiece with Ti-face, while the phase transformation and the number of dislocation in the Al layer are clearly decreased as increasing the TiN layer thickness. The surface morphology reveals that the sink-in phenomenon in indents has occurred in all samples with the change of TiN/Al surface orientations. Besides, the indents appear the sink-in for TiN layer thickness from 10 Å to 30 Å, and the pile-up is present in the indentation with TiN thicknesses of 50 Å and 70 Å. The atomic zone in the high stress–strain state is focused on the interface and around the indenter in all samples, and the interface acts as a barrier against the spread of stress and strain into the substrate interior. Furthermore, the atomic area in the high-temperature state is concentrated surrounding the indenter due to the friction between the substrate and indenter, and the deformation process of material from elastic to plastic causes the heat increase in the substrate

Microstructure evolution and coarsening kinetics of semisolid CuSn10P1 alloy under short-time isothermal treatment

The key success of semisolid rheology is to prepare high-quality semisolid slurries. To achieve that it is necessary to be able to characterize the microstructure, element distribution, and coarsening mechanism during short-time isothermal treatment. This present work applied the enclosed cooling slope channel (ECSC) to make a semisolid slurry of CuSn10P1 alloy. Effects of short-time isothermal treatment (0, 5, 10, 15, 20, 25 s) on microstructure characteristics, element distribution, grain stability, and coarsening kinetics of semisolid CuSn10P1 alloy were studied. The equiaxed or near-globular microstructure can be prepared and improved intergranular segregation of CuSn10P1 alloy through the semisolid slurry short-time isothermal treatment. The mean diameter of primary α-Cu phase gradually increases with soaking time prolonged, but shape factor shows a wavy trend. The mean size and shape factor changes caused by the instability of primary α-Cu phase during short-time isothermal treatment can be described by the melting mechanism and the coarsening mechanism. The relationship between the high Tin layer thickness of primary α-Cu and soaking time is consistent with the linear equation. The relationships of the Sn mass fraction in intergranular microstructure and primary α-Cu phase center versus soaking time are consistent with an exponential equation. The suitable isothermal treatment parameters for the semisolid CuSn10P1 alloy is the soaking time 15 s to 20 s at 990 °C.

Investigation on the performance of SnS solar cells grown by sputtering and effusion cell evaporation

SnS is an earth-abundant, non-toxic, and low-cost absorber material for solar cell applications. In this work, the physical properties of SnS thin films and efficiency of SnS solar cells were investigated for different tin metal layer thicknesses of 300 nm (Sn-300), 500 nm (Sn-500), and 700 nm (Sn-700) deposited by DC sputtering followed by the sulfurization using effusion cell evaporation method. The XRD and Raman characterizations confirmed the formation of single-phase SnS compound with orthorhombic structure for the case of Sn-500. The sulfurized films of Sn-500 had remarkable and homogeneous morphology with the optical band gap energy of 1.35 eV. The fabricated device showed an efficiency of 0.74% with an open-circuit voltage of 267mV, short circuit current density of 8.47 mA/cm2, and fill factor of 54.16. By varying the different metal tin layer thicknesses, this is the first report with device efficiency for SnS solar cells grown via effusion cell evaporation technique.

Characterization of the low temperature behavior of thin Titanium/Titanium Nitride multilayer films

Titanium and titanium nitride layers were alternately sputtered on a high resistivity silicon wafer to obtain a multilayer film structure, for a total thickness ranging between 34 and 180 nm. The electrical resistance of the Ti/TiN film was characterized from room temperature down to the superconducting transition. Both the resistivity just above the transition and the critical temperature were investigated as a function of the total film thickness and the single TiN layer thickness, respectively. The obtained resistivity range is 67–312 μΩ cm. Exploiting the proximity effect, we were able to tune the critical temperature in the 0.29–4.5 K range. A comparison between experimental data and theoretical models is proposed in order to facilitate the a priori design of superconducting detectors.

Effect of Cu Substrate Roughness and Sn Layer Thickness on Whisker Development from Sn Thin-Films.

The effect of copper substrate roughness and tin layer thickness were investigated on whisker development in the case of Sn thin-films. Sn was vacuum-evaporated onto both unpolished and mechanically polished Cu substrates with 1 µm and 2 μm average layer thicknesses. The samples were stored in room conditions for 60 days. The considerable stress—developed by the rapid intermetallic layer formation—resulted in intensive whisker formation, even in some days after the layer deposition. The developed whiskers and the layer structure underneath them were investigated with both scanning electron microscopy and ion microscopy. The Sn thin-film deposited onto unpolished Cu substrate produced less but longer whiskers than that deposited onto polished Cu substrate. This phenomenon might be explained by the dependence of IML formation on the surface roughness of substrates. The formation of IML wedges is more likely on rougher Cu substrates than on polished ones. Furthermore, it was found that with the decrease of layer thickness, the development of nodule type whiskers increases due to the easier diffusion of other atoms into the whisker bodies.