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Context and Background: The product of the electromagnetic (EM) wave’s power P times its period τ, i.e. Pτ, is the amount of energy conserved in EM wave’s absorption in matter. Whether Pτ is the amount of energy conserved in the emission of EM waves from matter is not assessed. Motivation: In this research, we perform a computational study to explore the ability of Pτ to represent the amount of energy conserved in EM wave’s emission from matter. Hypothesis: Since the magnitude of the power P of emitted EM waves computed through Larmor’s formula for a rotating dipole is excessively small, we alternatively hypothesize that Pτ and the law of conservation of energy can lead to a realistic estimation of P. Methods: We estimate the power PAME of the anomalous microwave emission (AME), a well-characterized radiation generated in the interstellar medium (ISM) by spinning dust grains, and one possible source of contamination of the cosmic microwave background (CMB). For our estimation of PAME, we assume the AME to be generated in a molecular cloud mostly populated by spinning silicate nanoparticles (SSNs) or polycyclic aromatic hydrocarbon (PAH) spinning dust grains. Indeed, SSNs and PAHs are listed among the most probable sources of AME, and their characteristics are well-known. We discriminate between realistic and non-realistic values of PAME based upon the magnitude of two parameters that depend on PAME: the significant distance z, and the time of photon production T. The parameter z is the space interval from the spinning dust grain within which the spinning dust grain’s electric field is effective. Results: Using the information available for AME, SSNs and PAHs, we estimate the power PAME using both Larmor’s formula and Pτ. We compare and comment the results obtained for z and T. Conclusions: Our study highlights the effectiveness of Pτ over Larmor’s formula in providing a realistic value of PAME. This finding might have consequences in quantum technology of single photon detection and production.

Context and background: A quantum formulation of vision in vertebrates was proposed in the early 1940s. The number of quanta useful for enabling vision was found. The time interval required for their absorption, however, was never specified. In the early 1950s, experimental data on the effects of light’s intensity increment on vision indicated that the quantum formulation is true only at low light’s intensities. In this case, a vaguely described signaling adaptation mechanism was invoked to explain the separation between vision at low and high intensities, accompanied by the switch from rod to cones as photoreceptors. Motivation: In this article, we want to prove the validity of the non-totally-quantum formulation and unveil the nature of the signaling adaptation mechanism. Hypothesis: To accomplish our proof, we hypothesize that the amount of energy transferred and conserved in light’s interaction with the eyes is given by the product of light’s intensity (or power) times its period. Method: We construct and use the plots of the trends of light’s intensity increments and the corresponding changes in the axon’s membrane capacitance versus adapting intensity. Results: We find that 1) the average solar light’s intensity is the critical value that separates low from high light’s intensity regimes in vision, and 2) changes in the capacitance of the axon’s membrane enable the signaling adaptation of vision when light’s intensity changes. Conclusions: We prove the validity of the non-totally-quantum formulation and unveil the nature of the signaling adaptation mechanism. Our proof is supported by the model based on light’s intensity times period as being the energy conserved in light-matter interaction This model suggests that 1) all the waves in the electromagnetic spectrum, at the correct intensity for each frequency, could be used to produce the effects of optogenetics in diagnostics and therapy, and 2) it takes seconds to minutes to see details in the dark when light is switched off.

There are numerous evidences that a relationship exists between the average power P of electromagnetic waves and the mechanical motion of the objects interacting with them. We investigate the effects of infrared (IR) light’s average power P on the transmission Fourier transform infrared (FTIR) spectra of thin cubic Yb2O3 and rhombohedral LaAlO3 films deposited on silicon via atomic layer deposition. We find that different values of P of the IR light displace the minima of the absorption bands. This effect is reproducible in different sets of experiments and in different spectrometers. To interpret the experimental findings, we use the law of conservation of energy. We find a correlation among the energy of the IR waves and the number, moment of inertia, and vibrational/rotational frequency of the bonds involved in the vibrational or rotational motion. The law of conservation of energy unveils that larger values of P of the IR light and lower wavenumbers of the resonances involve a larger number of crystal bonds. One practical application of our approach is that it suggests a way to improve the sensitivity of the FTIR spectra of thin crystalline films in the far IR region.

Context and Background: Recent research has shown that the amount of energy conserved in light-matter interaction is given by the product of light’s power P times its period τ , i.e. Pτ. To date, evidences of the validity of such finding are restricted to the interaction of light with capacitors, infrared spectroscopy, and vision in vertebrates. Motivation: In this article, we want to explore the validity of the role of Pτ in a broader range of phenomena. Hypothesis: We assume that the photothermoelectric (PTE) effect and photoredox catalysis reactions (PCRs) are manifestations of light-matter interaction and therefore have Pτ conserved in the process. Method: We take the data published in two articles, one on the PTE effect and the other on PCRs and revisit the data analysis of the authors of the original articles considering Pτ as the energy conserved. Results: In the case of the PTE effect, we unveil that the size of the light’s beam cross-sectional area impinging on the photodetectors plays a major role in defining the performance of the photodetectors. With our analysis, the photodetector responsivities actually turn out to be higher than those reported in the original article. In the case of the PCRs, we find that the magnitude of Pτ involved in successful PCRs is independent of the type of light used, whether near-infrared or blue. In addition, the involvement of Pτ in the description of PCRs helps to clarify the role of the law of conservation of energy, which was neglected by the authors of the original article. Conclusions: From this study, we infer that the hypothesis that Pτ that the hypothesis that represents the amount of energy conserved in light-matter interaction is valid and general, useful to measure device performance, and predict alternative processes to achieve desired outcomes.

It is common experience that our eyes do not perceive significant changes in color when we observe for long time an object continuously exposed to light. We always see plants to be green in summer until in autumn factors external to our vision, such as changes in the length of daylight and temperature, cause the break-down of chlorophyll and, in turn, spectacular changes in plant’s colors. Likewise, the photocurrent produced in solar panels or field effect transistors achieves a steady state magnitude shortly after the start of the illumination. The steady state photocurrent lasts until the illumination stops. Understanding the origin of the steady state response of a device or light harvesting (LH) system to illumination with electromagnetic (EM) waves motivates the research presented in this work. In our experiments, we used capacitors as LH systems and illuminated them with infrared (IR) light over an 80 hours time period. We investigated the interaction between light and matter by monitoring versus time the voltage output of the capacitors. By combining modeling and experimental observations, we concluded that the steady state voltage is established soon after the start of the illumination as the consequence of the law of conservation of energy. We also found that the magnitude of the voltage in the steady state depends on the power and period of the illuminating IR light, and on the capacitance of the capacitor. When light’s power undergoes fluctuations, also the voltage produced by the capacitor and the surface charge density on the capacitors do so. These findings suggest that the law of conservation of energy has a significant repercussion when light is absorbed by matter in the steady state, for example in the mechanism of vision in vertebrates. Likewise, these findings are true when light is emitted from matter, for example in the mechanism of formation of the Cosmic Microwave Background (CMB).

The wave-particle duality of light is a controversial topic in modern physics. In this context, this work highlights the ability of the wave-nature of light on its own to account for the conservation of energy in light-matter interaction. Two simple fundamental properties of light as wave are involved: its period and its power P. The power P depends only on the amplitude of the wave’s electric and magnetic fields (Poynting’s vector), and can easily be measured with a power sensor for visible and infrared lasers. The advantage of such a wave-based approach is that it unveils unexpected effects of light’s power P capable of explaining numerous results published in current scientific literature, of correlating phenomena otherwise considered as disjointed, and of making predictions on ways to employ the electromagnetic (EM) waves which so far are unexplored. In this framework, this work focuses on determining the magnitude of the time interval that, coupled with light’s power P, establishes the energy conserved in the exchange of energy between light and matter. To reach this goal, capacitors were excited with visible and IR lasers at variable average power P. As the result of combining experimental measurements and simulations based on the law of conservation of energy, it was found that the product of the period of the light by its power P fixes the magnitude of the energy conserved in light’s interaction with the capacitors. This finding highlights that the energy exchanged is defined in the time interval equal to the period of the light’s wave. The validity of the finding is shown to hold in light’s interaction with matter in general, e.g. in the photoelectric effect with x-rays, in the transfer of electrons between energy levels in semiconducting interfaces of field effect transistors, in the activation of photosynthetic reactions, and in the generation of action potentials in retinal ganglion cells to enable vision in vertebrates. Finally, the validity of the finding is investigated in the low frequency spectrum of the EM waves by exploring possible consequences in microwave technology, and in harvesting through capacitors the radio waves dispersed in the environment after being used in telecommunications as a source of usable electricity.

The interaction between infrared radiation and a power generator device in time is studied as a route to harvest infrared, and possibly other electromagnetic radiations. Broadening the spectrum of the usable electromagnetic spectrum would greatly contribute to the renewable and sustainable energy sources available to humankind. In particular, low frequency and low power radiation is important for applications on ships, satellites, cars, personal backpacks, and, more generally, where non-dangerous energy is needed at all hours of the day, independent of weather conditions. In this work, we identify an electric and an entropic contribution to the energy transfer from low power infrared radiation to the power generator device, representing electrical and thermal contributions to the power generation. The electric contribution prevails, and is important because it offers multiple ways to increase the voltage produced. For example, placing black-colored gaffer tape on the illuminated face doubles the voltage produced, while the temperature difference, thus the entropic contribution, is not sensitive to the presence of the tape. We recognize the electric contribution through the fast changes it imparts to the voltage output of the power generator device, which mirror the instabilities in time of the infrared radiation. The device thus acts as sensor of the infrared radiation’s behavior in time. On the other hand, we distinguish the entropic contribution through the slow changes it causes to the voltage output of the power generator device, which reflect the relative delay with which the two faces of the device respond to thermal perturbations.

Upon formation, radiative polaritons in thin oxide films or crystals emit radiation to the surrounding space. This radiation is confined in a small range of the microwave to far-infrared region of the electromagnetic spectrum, independently of the oxide chemistry. This work shows that the low-frequency radiation is blackbody radiation associated with a temperature directly related to the boson character of the radiative polaritons and to their amount. The proximity of this temperature to absolute zero Kelvin explains the confinement of the frequency. This phenomenon is named polariton evaporation.

The Seebeck coefficient S is a temperature- and material-dependent property, which linearly and causally relates the temperature difference △T between the “hot” and “cold” junctions of a thermoelectric power generator (TEC-PG) to the voltage difference △V. This phenomenon is the Seebeck effect (SE), and can be used to convert waste heat into usable energy. This work investigates the trends of the effective voltage output △V(t) and effective Seebeck coefficient S'(t) versus several hours of activity of a solid state TEC-PG device. The effective Seebeck coefficient S'(t) here is related to a device, not just to a material’s performance. The observations are pursued in an insulated compartment in various geometrical and environmental configurations. The results indicate that the SE does not substantially depend on the geometrical and environmental configurations. However, the effective Seebeck coefficient S'(t) and the produced effective △V(t) are affected by the environmental configuration, once the temperature is fixed. Heat transfer calculations do not completely explain this finding. Alternative explanations are hypothesized.

The mechanism that activates a bi-junction power generator under the effects of heat is the Seebeck effect, that is, the production of voltage difference ΔVt is directly proportional to the temperature difference ΔTt between the "hot" and "cold" junctions of the device. This phenomenon is well established and is known as thermoelectric power generation. Here, it is shown that, instead, the causal and linear relationship between ΔVt and ΔTt is lost when continuous broadband infrared CB-IR radiation illuminates a bi-junction power generator in an insulated compartment. The observed phenomenon is IR power generation. Heat transfer calculations fail in explaining the experimental trends. The interaction between CB-IR radiation and the charge carriers in the bi-junction power generator might play a role in the ΔVt production, depending upon the geometry of the experimental setup. The longitudinal propagation of collective oscillations, for example, polaritons, in the plates protecting the "hot" and "cold" junctions of the bi-junction power generator could explain the ΔVt production and the characteristic time constants. The findings should be considered in the design, fabrication, and improvement of thermopiles, power meters, and IR energy-harvesting devices. © 2013 Wiley Periodicals, Inc. Complexity 19: 44-55, 2014

Nanostructured surfaces are finding use in several medical applications, including tissue scaffolds and wound dressings. These surfaces are frequently manufactured from biocompatible polymers that are susceptible to ultraviolet (UV) damage. Polyethersulfone (PES) is a biocompatible polymer that undergoes oxidation and degradation when exposed to ultraviolet (UV) light. A uniform TiO2 coating can protect PES during exposure to UV sources (e.g., germicidal lamps and sunlight). The goal of this study was to determine whether atomic layer deposition (ALD) can successfully be used to grow TiO2 onto PES, protect it from UV irradiation, and reduce macrophage in vitro cytotoxicity. TiO2 was ALD-coated onto PES at 21 nm thickness. Uncoated PES exposed to UV for 30 min visibly changed color, whereas TiO2-coated PES showed no color change, indicating limited degradation. Macrophages exposed to UV-treated PES for 48 h showed reduced cell viability (via MTT assay) to 18% of control. In contrast, the cell viability for UV-treated TiO2-coated PES was 90% of control. Non-UV treated PES showed no decrease in cell viability. The results indicate that ALD of TiO2 thin films is a useful technique to protect polymers from UV damage and to retain low cytotoxicity to macrophages and other types of cells that are involved in wound healing. TiO2- coated PES membranes also have potential use in direct methanol fuel cells and in wastewater treatment membranes.

Light-matter interaction involving photons with large period τ of ~ 3 fs (10 -15 s) and above, i.e. infrared (IR) to microand radio-waves, displays interesting properties so far mostly unexplored. These photons indeed can produce voltages after activating charges or currents. For example, in the literature it is demonstrated that animals and plants neural system (which is similar to a system consisting of capacitors in series) can be stimulated by IR photons. Additionally, radio waves can activate currents in antennas. However, a systematic investigation of the voltages and currents produced, of the charge density changes, and of the number of photons involved is missing. Here we initiate the investigation of the voltages produced by a capacitor-type device. We shine broadband IR light in the middle IR region (MIR) at a power of 25 mW onto capacitors with capacitance C from 30 to 300 pF. We observe that the voltage produced increases with decreasing C while developing negligible temperature changes. Further increases can be obtained by increasing τ and, modestly, by deviating from normal incidence the angle of incidence θ between the IR light and the illuminated plate of the capacitor. Specifically, here we compare τ in the MIR and far IR (FIR) regions, and θ from 0° (normal incidence) to 45°. The effects of the power of the light will be explored in the near future. These results suggest that it is possible to harvest and transform IR, micro- and radio-waves into usable and sustainable electricity.

This project studies the basic processes involved in the interaction of infrared radiation with matter and, in this effort, establishes a method to harvest infrared radiation and transform it into usable energy. We have identified an electrical contribution to the energy transfer from the infrared radiation to the device we use to harvest it. This device behaves as a capacitor, and we found a way to triplicate the voltage generated by the device when exposed to the infrared radiation. This significant increase can be obtained by placing two devices in series and covering the surface of the device facing the infrared radiation to tape, which modifies the capacitance of the device. We plan on modeling the interaction of the infrared radiation with our device using the conjugated variable-based approach. We also plan on studying the current produced by the device to increase efficiency in power generation. We are also looking into other alternative device designs to fabricate nano- and macro-power generation device. Seven undergraduate students were involved in the research and the research inspired an approach to Thermodynamics and Statistical Mechanics related to the conjugated variable-based approach.

A variety of biologically-derived hemostatic agents,including cellulose, bone wax, chitosan, collagen,and gelatin, have been utilized over the years forreducing blood loss associated with trauma [1,2].Ahemostatic agent should exhibit several properties,including (a) the ability to stop hemorrhage fromarterial and/or venous sources in a short time peri-od, (b) usability with minimal training, (b) lowweight, (c) high stability, (d) low cost, (e) and bio-compatibility (e.g., absence of cytotoxicity) [1–7].There are several benefits to the use of plant-derived materials such as cellulose in hemostasisapplications,including an absence of disease trans-mission from donor to recipient and an absence ofantibody formation to coagulation factors [8]. Cel-lulose is a wood pulp-derived material that hasbeen utilized in hemostasis for over 60 years;use ofoxidized cellulose, oxidized regenerated cellulose,carboxymethylcellulose, and cellulose acetate hasbeen described [1, 9–12]. In addition, these porous,water-absorbable materials do not need to be re-moved after use because they are degraded withinthe body over several weeks,increasing patient sat

In situ characterization of low temperature atomic layer deposition (ALD) of ZnO and aluminum-doped ZnO (ZnO:Al) establishes a relationship between species adsorption, mass uptake, and surface electrical conductance during deposition and dopant atom incorporation. Conductance measured in situ during ZnO ALD oscillates with species surface adsorption, consistent with surface potential modulation and charge transfer during surface reaction. Dopant introduction using trimethylaluminum impedes both surface potential modulation and film growth, and a reaction scheme involving surface proton exchange complexes is presented to understand the observed results. Electronically active doping is achieved only after Al species transition four to five monolayers into the film bulk, consistent with a nonuniform dopant atom distribution in the direction of film growth. Results have important implications in understanding relations between dopant incorporation, activation, and film growth mechanisms in atomic layer deposi...

Aluminum incorporation into ZnO films during atomic layer deposition (ALD) is investigated using in situ quartz crystal microbalance and electrical conductance analysis. Chemical interactions between Zn and Al species during ZnO:Al ALD depend on the order of metal precursor exposure. Exposing the growing ZnO surface to trimethyl aluminum (TMA) impedes the subsequent ∼4 monolayers of ZnO growth. However, the extent of interaction can be reduced by performing the TMA exposure immediately following a diethyl zinc step, without an intermediate water exposure step, consistent with increased surface mixing of Zn and Al species. Infrared spectroscopy analysis of heavily aluminum doped ZnO shows features consistent with the presence of amorphous ZnAl2O4 bonding units. For more lightly doped films, mass spectroscopic depth profiling confirms nonuniform aluminum distribution, even after annealing at 500 °C. Film conductance measured during growth shows complex trends that are highly repeatable over multiple doping ...

Three-dimensional nanoscale constructs are finding applications in many emerging fields, including energy generation and storage, advanced water and air purification, and filtration strategies, as well as photocatalytic and biochemical separation systems. Progress in these important technologies will benefit from improved understanding of fundamental principles underlying nanostructure integration and bottom-up growth processes. While previous work has identified hydrothermal synthesis conditions to produce nanoscale ZnO rods, sheets, and plates, strategies to systematically integrate these elements into more complex nano-architectures are not previously described. This article illustrates that amorphous nanoscale coatings formed by atomic layer deposition (ALD) are a viable means to modulate and screen the surface polarity of ZnO crystal faces and thereby regulate the growth morphology during successive hydrothermal nanocrystal synthesis. Using this new strategy, this work demonstrates direct integration and sequential assembly of nanocrystalline rods and sheets to produce complex three-dimensional geometric forms, where structure evolution is achieved by modifying the surface growth condition, keeping the hydrothermal growth chemistry unchanged. Therefore, rational planning of seed layer and feature spacing geometries may allow researchers to engineer, at the nanoscale, complex three-dimensional crystalline and semicrystalline constructs for a wide range of future applications.

The antifungal properties of two silver-coated natural cotton fiber structures prepared using a supercritical carbon dioxide (scCO2) solvent were examined. Scanning electron microscopy confirmed that the scCO2 process may be used to produce cotton fiber textiles with uniform silver nanoparticle coatings. A version of the Kirby-Bauer disk diffusion test was used to assess the ability of these textiles to inhibit fungal growth. Cotton fabric samples modified with Ag(hepta) and Ag(cod)(hfac) exhibited measurable zones of inhibition. On the other hand, the uncoated fabric had no zone of inhibition. Possible applications of antifungal textiles prepared using scCO2 processing include use in hospital uniforms and wound dressings.

The uncontrolled formation of an interfacial layer between high-κ oxides and semiconductors is a major concern in advanced microelectronics not only for Si-based devices but also for those exploiting the higher mobility of Ge and GaAs. Using transmission electron microscopy, the authors investigate the interfacial layer formed between as-grown thin Al2O3 films, deposited using atomic layer deposition, and oxide free Si(100), Ge(100), and GaAs(100). In particular, they compare the effects of two different oxygen sources (H2O and O3) on interfacial layer formation during the growth process. They show that no interfacial layer can be distinguished unambiguously between the Al2O3 films, grown using TMA and H2O or O3, and all the semiconductor substrates.

X-ray diffraction and infrared spectroscopy measurements are conducted in order to assess the crystallographic structure and chemical purity of lanthanum oxide (La2O3) films grown by atomic layer deposition (ALD) on Si substrates. In situ capping with thin aluminum oxide (Al2O3) layer is proved to be beneficial in preventing the formation of lanthanum hydroxide phases. The effect of two process parameters, namely, La2O3 film growth temperature (260–500°C range) and postdeposition annealing temperature (600–1100°C range), on the chemical and structural evolutions of Al2O3∕La2O3∕Si stacks is discussed. This study enables the identification of the optimum ALD growth recipe yielding the highest hexagonal La2O3 phase content, which might be suitable for integration into innovative metal oxide semiconductor devices.

We report on the atomic layer deposition (ALD) of MnO and NiO thin films on Si(100) using Mn(EtCP)(2) [EtCp = ethylcyclopentadienyl, (C2H5)C5H4] and Ni(EtCp)(2) in the temperature range of 150-300 degrees C. H2O or O-3 is selected as oxygen source for the depositions. The growth temperature (T-g) and oxygen source impact on the structure, electronic density, and impurity concentration for the as-grown MnO and NiO films have been studied using X-ray reflectivity, (XRR), grazing incidence X-ray diffraction (GIXRD), and Fourier transform infrared (FTIR) spectroscopy. A steady growth rate of 0.024-0.025 nm/cycle for the films grown using Mn(EtCP)(2) and H2O was observed in the T-g range of 250-300 degrees C. FTIR does not show any carbon impurities in the MnO films grown with H2O. The films grown using Mn(EtCp)(2) and O-3 at 300 degrees C exhibit poor adhesion on Si(100). NiO films with low amounts of contaminants are achieved using O-3 and at a T-g of 250 degrees C or above. The growth rate, however, is very high for films deposited at T-g = 150 degrees C and decreases significantly in films deposited at higher temperatures. In addition, no film growth was observed for the Ni(EtCp)(2)/H2O process. The as-grown MnO and NiO films prepared using H2O and O-3 as oxidizer, is shown, by GIXRD a polycrystalline cubic structure. (C) 2008 Published by Elsevier B.V.

Atomic Layer Deposition (ALD) has gained increasing attention for the sub-nm growth of high permittivity (k) rare earth oxide films. State of the art device operation heavily depends on the oxide/semiconductor interface properties. In this work, we address mainly through HRTEM-EELS experiments interface issues for ALD-grown Lu2O3/Si and La2O3/Si interfaces. Complementary results from GIXRD and electrical measurements on selective samples are presented. We show that, after exposure to air, Lu2O3 films capped with an Al2O3 layer are essentially free of interfacial layer formation, even if the starting Si surface is chemically oxidized. We also demonstrate that the La2O3 film reactivity with Si can be controlled up to a certain extent by appropriately choosing the ALD precursor combination. In particular, the La(Cp)3+O3 scheme favours over the La(Cp3)+H2O one in terms of a (i) smaller low-k interfacial layer thickness and interface trap density and (ii) stabilization of the high-k hexagonal La2O3 phase.

The synthesis and the characterization of dielectrics with very high and very low relative permittivity k, are one of the challenges for scaling the dimensions of microelectronic devices. It will be shown that unique and useful insight on high k thin films and about the surface termination of internal buried empty space (k = 1) can be obtained by combining different positron annihilation spectroscopies. Characterization of nano-cavities in Si and of HfO2 high k thin films will be presented and discussed. (c) 2006 Elsevier Ltd. All rights reserved.

Infrared power generation (IRPG) consists of shining infrared (IR) radiation on a power generator (PG) device and collecting a usable voltage. The PI and Co-PI are actively pioneering the effort of understanding and implementing IRPG. Scientifically. the primary objective of this Project is to unveil the mechanisms alternative to the Seebeck effect contributing to voltage production in IRPG. This task implies establishing and assessing the equivalence or lack thereof among radiative heat transfer, on one hand, and convective and conductive heat transfer, on the other. Some possible consequences of such an equivalence or lack thereof in the fields of device physics, astronomy and geology, biology and medicine and art, are discussed.

Infrared radiation is used to radiatively transfer heat to a nanometric power generator (NPG) device with a thermoelectric Nb-doped TiO2 film deposited by atomic layer deposition (ALD) as the active element, onto a borosilicate glass substrate. The linear rise of the produced voltage with respect to the temperature difference between the “hot” and “cold” junctions, typical of the Seebeck effect, is missing. The discovery of the violation of the Seebeck effect in NPG devices combined with the ability of ALD to tune thermoelectric thin film properties could be exploited to increase the efficiency of these devices for energy harvesting purposes.

X-ray photoelectron spectroscopy (XPS) was used to investigate the band alignment of lutetium oxide films with a germanium substrate. Lu2O3 films were grown on Ge (100) by atomic layer deposition. The conduction- (CBO) and valence- (VBO) band offsets of the Lu2O3/Ge heterojunction were determined to be 2.2 +/- 0.1 and 2.9 +/- 0.1 eV respectively. Internal photoemission measurements performed on metal-oxide-semiconductor devices gave a CBO of 2.1 +/- 0.1 eV and a VBO of 3.0 eV, in excellent agreement, within the experimental error, with the values obtained by XPS. Copyright (C) 2006 John Wiley & Sons, Ltd.

The single crystal X-ray diffraction study of [(η5-C5H4SiMe3)2LuCl]2, prepared from LuCl3 and Na[C5H4SiMe3], shows the compound to be a centrosymmetric dimer with two η5-bonded cyclopentadienyl rings and two symmetrically bridging chlorine atoms coordinated to each of the two metal centers. The coordination geometry around the lutetium atoms is that of a distorted pseudo tetrahedron. The Lu-C(Cp) distances lie within the narrow range of 2.571 - 2.608 Å . The Lu-Cl bond lengths are 2.639(1) and 2.653(1) Å . The crystal structure shows no significant intermolecular contacts.

Understanding and optimizing electrical and structural properties of high- κ oxides are key steps in view of their application as SiO 2 substitutes in CMOS devices. In this work, we address the effects of growth temperature ( T g ,) post-deposition annealing and substrate preparation on the structural, compositional, and electrical properties of thin films (≈13 nm thick), deposited on p-type Si(1 0 0)/SiO 2 (chemical oxide) by atomic layer deposition (ALD). In particular, we investigate the effects of: (1) different T g (150, 250 and 350 °C); (2) rapid thermal annealing at 950 °C in N 2 for 60 s; and (3) substrate in situ heat treatment before growth and longer pulses at the beginning of the deposition.

In this paper we investigate interface evolution upon annealing in O2 by means of X-ray reflectivity and spectroscopic ellipsometry on HfO2 and ZrO2 thin films deposited with atomic layer deposition (ALD) on Si (100). The analysis of SE data is made with a common optical model adjusting the layer thickness and the surface and interface roughness, while thickness and interface composition are extracted from XRR data by means of the matrix method. The poor electron density contrast between SiOs and Si as opposed to the strong one between HfO2/ZrO2 and Si makes the extraction of structural data from XRR data extremely difficult. Information on interdiffusion phenomena occurring between the high-κ layer and the interfacial SiO2 can be obtained, while SiO2 growth is hardly detectable.

Zirconium dioxide is one of the candidates for substitution of SiO2 as dielectric gate in complementary metal-oxide-semiconductor devices. In this work, 64 and 107 nm thick ZrO2 films were grown on Si(100) using atomic layer deposition, which produces uniform and conformal layers, as required in microelectronics. Structural investigation was made using ultra-violet Raman spectroscopy and far-infrared transmission spectroscopy. With the use of a 5.0 eV excitation in Raman spectroscopy thin films can be measured because of the enhancement of the Raman efficiency, the reduction of the photoluminescent background, and the elimination of the signal of the silicon substrate. Far-infrared spectroscopy reveals also information on the material structure because in the 100-700 cm-1 frequency range the infrared radiation resonates with optical phonons. The strength and absorption frequency of the latter depend indeed on the details of the material structure. From our work we conclude that the relative amount of tetragonal and monoclinic phases in the ZrO2 films changes with film thickness and annealing procedure. The observed trend suggests that the increase of the thickness of the film, as well as the thermal annealing at 950 °C for 30 s, produce an increase of the relative amount of the monoclinic phase. © 2003 Elsevier B.V. All rights reserved.

Zirconium dioxide films are grown in 200 atomic layer deposition cycles. Zirconium tetrachloride (ZrCl4) and water (H2O) are used as precursors. A relatively high dielectric constant (κ=22), wide band gap, and conduction band offset (5.8 and 1.4 eV, respectively) indicate that zirconium dioxide is a most promising substitute for silicon dioxide as a dielectric gate in complementary metal–oxide–semiconductor devices. However, crystallization and chlorine ions in the films might affect their electrical properties. These ions are produced during atomic layer deposition in which the ZrCl4 precursor reacts with the growth surface. It is desirable to tune the composition, morphology, and structural properties in order to improve their benefit on the electrical ones. To address this issue it is necessary to properly choose the growth parameters. This work focuses on the effects of the growth temperature Tg. ZrO2 films are grown at different substrate temperatures: 160, 200, 250, and 350 °C. Relevant modification of the film structure with a change in substrate temperature during growth is expected because the density of reactive sites [mainly Si+1–(OH)−1 bonds] decreases with an increase in temperature [Y. B. Kim et al., Electrochem. Solid-State Lett. 3, 346 (2000)]. The amorphous film component, for example, that develops at Si+1–(OH)−1 sites on the starting growth surface, is expected to decrease with an increase in growth temperature. The size and consequences of film property modifications with the growth temperature are investigated in this work using x-ray diffraction and reflectivity, and atomic force microscopy. Time of flight-secondary ion mass spectrometry is used to study contaminant species in the films. From capacitance–voltage (CV) and current–voltage (IV) measurements, respectively, the dielectric constant κZrO2 and the leakage current are studied as a function of the film growth temperature.

Electrically detected magnetic resonance (EDMR) spectroscopy has been used to investigate the interfaces between Si(1 0 0) and the high- k dielectrics Al 2 O 3 and ZrO 2 grown by atomic layer deposition, with or without the native oxide removed. The experimental results show that the dominant electrically active defects at these interfaces are an isotropic center, typical of the disordered silicon dangling bond, and a trigonal center, P b0 -like, known from the Si/SiO 2 interface. This shows that the paramagnetic defects also at nominally abrupt interfaces between Si and these high- k dielectrics are Si/SiO 2 -like. Deconvolution showed that the difference between g ⊥ and g || for the Si/ZrO 2 interfaces is slightly larger then for the Si/Al 2 O 3 interfaces.

S- and p-polarized middle infrared reflection spectra of a 0.25 μm thick TiO 2 film on silicon are measured with beam angle of incidence of φ =45° and 75°. An inversion of the absorption band related to the high frequency maximum of the loss function −1/Im[ ϵ ( ν )] of TiO 2 occurs while changing φ in the spectra measured using a p-polarized infrared beam. This inversion does not take place for TiO 2 films grown on aluminum. The phenomenon is studied calculating the spectra with Fresnel and Fuchs–Kliewer reflection coefficients. The former considers real substrates with finite and non-zero conductivity, while the latter considers ideal substrates with infinite and zero conductivity. Our study shows that the effect of the damping factor of the ion oscillations in TiO 2 has to be taken into account to explain the observed phenomenon. We conclude that the inversion of the absorption band related to the high frequency maximum of the loss function −1/Im[ ϵ ( ν )] of TiO 2 is due to the finite but low conductivity of the silicon substrate.

The polarization-dependent optical response of vitreous titanium dioxide films was determined by infrared reflection–absorption spectroscopy (IRAS). The predominant nearest-neighbor coordination (short-range order) in the films was characteristic of crystalline anatase. A dielectric function e(ν) was constructed, based on random orientational disorder of anataselike, octahedral TiO6 units relative to the substrate. This dielectric function, which is the directional average of the dielectric function for an anatase crystal in the E⊥c and E∥c orientations, was used to calculate energy loss functions from which theoretical IRAS spectra were obtained. Experimental absorption band frequencies are in good agreement with peaks in the calculated transverse optic loss function, Im[e(ν)], at 261 and 436 cm−1, and in the calculated longitudinal optic loss function, Im[−1/e(ν)], at 840 cm−1. Agreement (i.e., polarization-dependent behavior, band frequency, and relative intensity) between the experimental and theoretical IRAS spectra indicates that orientational disorder of TiO6 units is the important factor governing infrared reflection–absorption behavior of the films.

Infrared (IR) power generation is emerging as a useful method to harvest IR light and transform it into usable energy available day and night. Here, the authors continue the effort to fabricate thin thermoelectric TiO2/TiN nanolaminate films via atomic layer deposition (ALD) and, specifically, focus on the effects of film sheet resistance Rs on the voltage produced by nanopower generator devices with these films as their active elements. By changing the number and the thickness of the TiO2/TiN nanolaminate, the authors control the sheet resistance Rs over 3 orders of magnitude. The authors observe that the voltage produced by nanopower generator devices increases with Rs and exhibits two roughly linear regimes. In the first regime, when Rs 1 kΩ/◻, where the slope characterizing the increase of voltage with sheet resis...

Titania is a material with structural flexibility, and as a result, readily forms both crystalline polymorphs and an amorphous structure in thin films grown near room temperature. The goal of this study is to correlate fundamental optical absorption edge characteristics with the phase constituency of titania films. To that end, films with coexistent rutile, anatase, and amorphous constituents were sputter deposited onto fused silica and 〈111〉-Si substrates. The films were then subjected to cyclic annealing in air at moderate temperature (700 and 1000 °C) to affect phase changes. Bragg–Brentano x-ray diffraction was used for phase identification and near ultraviolet-visible transmission and reflection spectrophotometry was used to determine the optical absorption coefficient at the onset of interband transitions. The optical absorption coefficient was modeled within the framework of the coherent potential approximation (CPA), with Gaussian site disorder introduced into the valence and conduction bands of a...

An extensive evaluation of the electronic structure of the Ag(110) C 60 interface is reported as a function of the overlayer coverage. Submonolayer coverages are characterized by a strong chemical adlayer-substrate interaction which causes a significant re-distribution of the π-symmetry occupied and π ∗ - and σ ∗ - symmetry unfilled molecular states local to the C sites. This is consistent with a two-dimensional array of C 60 molecules. For coverages ≥ 1 ML, traces of three-dimensional coalescence are found with an electronic structure very close to solid fullerene.

Through simulations, this work explores the effects of conducting, semiconducting, and insulating substrates on the absorption of infrared radiation by radiative polaritons in oxide layers with thicknesses that range from 30 nm to 9 μm. Using atomic layer deposition, oxide layers can be formed in the nanometer scale. Our results suggest that the chemistry and conductivity of the substrate determine the amount of absorption by radiative polaritons in oxide layers thinner than the skin depth. The effects of the chemistry and conductivity of the substrate are especially effective for oxide films thinner than about 250 nm, which we label as the substrate sensitive thickness of the oxide film.

Atomic layer deposition (ALD) growth of high-κ dielectric films (ZrO2 and HfO2) was performed using ZrCl4, HfCl4, and H2O as precursors. In this work, we use time of flight secondary ion mass spectrometry to investigate the chlorine distribution in ALD grown ZrO2 and HfO2 films, and its evolution during rapid thermal processes in nitrogen atmosphere. Chlorine outdiffusion is found to depend strongly upon annealing temperature and weakly upon the annealing time. While in ZrO2 chlorine concentration is significantly decreased already at 900 °C, in HfO2 it is extremely stable, even at temperatures as high as 1050 °C.

Thermally robust monolayers of 4-6 nm diameter FePt nanoparticles (NPs) were fabricated by combining chemical synthesis and atomic layer deposition. Spin-cast monolayers of FePt NPs were coated with thin, 11 nm-thick layers of amorphous Al(2)O(3), followed by annealing to convert the FePt NPs from an alloy (A1) into intermetallic FePt (L1(0)) and FePt(3) (L1(2)) phases. The Al(2)O(3) layer serves as a barrier that prevents sintering between NPs during annealing at temperatures up to 730 °C. Electron and X-ray diffraction in conjunction with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) show that as-synthesized A1 FePt NPs convert into L1(0) and L1(2) phase NPs through annealing. HAADF-STEM measurements of individual NPs reveal imperfect ordering and show that the NP composition determines which intermetallic phase is obtained. Mixed-phase NPs with L1(0) cores and FePt(3) L1(2) shells were also observed, as well as a smaller number of unconverted A1 NPs. These results highlight the need for improved control over the compositional uniformity of FePt NPs for their use in bit-patterned magnetic recording.

It is demonstrated here that nonresonant Raman spectroscopy can be used for unequivocal determination of short-range order in ultrathin films, using different structures of titanium dioxide as the model system. Titania films as thin as 7 nm sputter deposited on 〈111〉 Si have been analyzed and their phase content determined.

Anatase TiO2 films are grown on Si (100) by atomic layer deposition. Three different interlayers (Si3N4, Al2O3, and Ti-rich SiOx) between the TiO2 films and the Si substrate have been considered. The band alignment of the titanium oxide films with the silicon substrate is investigated by x-ray photoelectron spectroscopy (XPS), internal photoemission (IPE) spectroscopy, and optical absorption (OA) measurements. XPS analysis indicates that TiO2/Si heterojunctions with different interlayers (ILs) have different valence-band offsets (VBOs). A VBO value of 2.56 +/- 0.09 eV is obtained for the TiO2/Ti-rich SiOx/Si sample. Similarly, we obtain a VBO value of 2.44 +/- 0.09 and 2.73 +/- 0.10 eV for the TiO2/Si3N4/Si and TiO2/Al2O3/Si samples, respectively. According to IPE and OA measurements, the band gap of the as-grown TiO2 films is 3.3 +/- 0.1 eV for all the samples. Combining the XPS and IPE data, the conduction band offset values at the TiO2/Si heterojunction are found to be -0.2 +/- 0.1, -0.4 +/- 0.1, and -0.5 +/- 0.1 eV for the TiO2/Si3N4/Si, TiO2/Ti-rich SiOx/Si, and TiO2/Al2O3/Si samples, respectively. According to our experimental results, the band alignment of a TiO2 film with the underlying Si (100) substrate is clearly affected by the presence of an IL, suggesting the possibility to tune the band structure of a TiO2/Si heterojunction by selecting the proper IL. (c) 2008 American Institute of Physics.

NiO films were grown on Si(100) by atomic layer deposition using Ni(Cp)(2) (Cp=cyclopentadienyl, C5H5) or Ni(EtCp)(2) [EtCp=ethylcyclopentadienyl, (C2H5)C5H4)] and ozone in the 150-300 degrees C temperature range. The growth temperature dependence of structure, electronic density, and impurity levels for the prepared NiO films was studied using X-ray reflectivity, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, time of flight-secondary ion mass spectroscopy (ToF-SIMS), and transmission electron microscopy. The behavior of films deposited using Ni(Cp)(2) and Ni(EtCp)(2) is compared and discussed. NiO films with good stoichiometry and low amounts of contaminants are obtained at a growth temperature (T-g) of 250 degrees C or above. At a fixed T-g, the growth rate for NiO films deposited using Ni(Cp)(2) is higher than the one of films deposited using Ni(EtCp)(2). Furthermore, the growth rate for NiO deposited using Ni(Cp)(2) at T-g = 150 degrees C is 0.32 nm/cycle and decreases substantially in films deposited at higher temperatures. The electronic density of NiO films deposited at 300 degrees C is close to the one of bulk NiO (1.83 e(-)/A(3)). According to XRD and FTIR results, films deposited at T-g >= 200 degrees C have a simple cubic polycrystalline structure. Impurities in NiO films decrease with increasing T-g, as detected by ToF-SIMS.

Rare earth oxides (REOs) have lately received extensive attention in relation to the continuous scaling down of non-volatile memories (NVMs). In particular, La2O3 films are promising for integration into future NVMs because they are expected to crystallize above 400 degrees C in the hexagonal phase (h-La2O3) which has a higher K value than the cubic phase (c-La2O3) in which most of REOs crystallize. In this work, La2O3 films are grown on Si by atomic layer deposition using La(C5H5)(3) and H2O. Within the framework of the h-La2O3 formation, we systematically study the crystallographic evolution of La2O3 films versus annealing temperature (200-600 degrees C) by Fourier transform infrared spectroscopy (FTIR) and grazing incidence X-ray diffraction (GIXRD). As-grown films are chemically unstable in air since a rapid transformation into monoclinic LaO(OH) and hexagonal La(OH)(3) occurs. Vacuum annealing of sufficiently thick (> 100 nm) La(OH)(3) layers induces clear changes in FTIR and GIXRD spectra: c-La2O3 gradually forms in the 300-500 degrees C range while annealing at 600 degrees C generates h-La2O3 which exhibits, as inferred from our electrical data, a desirable k similar to 27. A quick transformation from h-La2O3 into La(OH)(3) occurs due to H2O absorption, indicating that the annealed films are chemically unstable. This study extends our recent work on the h-La2O3 formation. (C) 2008 Elsevier B.V. All rights reserved.

The physical, chemical, and electrical properties of various high-κ oxides deposited using atomic layer deposition (ALD) on Ge and GaAs are presented. The choice of precursor combination for ALD, as well as the semiconductor surface preparation before film deposition, play a significant role in tailoring the properties of the high-κ oxide stacks. The results obtained for HfO2, Lu2O3, and Al2O3 high-κ oxides are discussed and compared, when possible, with those reported in the literature for films grown using various deposition techniques. A review of the available data on the band offset of high-κ oxides deposited on Ge and GaAs is also presented.

Good quality and perfectly stoichiometric GeO2 layers are promising interlayers to be implemented in alternative devices based on high dielectric constant oxide/Ge(100). In this work, the authors report on the growth by atomic layer deposition of GeO2 films using a divalent Ge precursor combined with O-3. The films are composed of smooth and perfectly stoichiometric GeO2. The contamination level is extremely low. The deposited GeO2 films have a band gap of 5.81 +/- 0.04 eV. The conduction and valence band offsets at the GeO2/Ge heterojunction are found to be 0.6 +/- 0.1 and 4.5 +/- 0.1 eV, respectively.

La2O3 films are obtained by annealing in vacuum La(OH)(3) layers produced upon air exposure of La2O3 layers grown using atomic layer deposition. Sample thickness determines whether hexagonal or cubic La2O3 form. The observed infrared active phonon mode with minimum frequency for hexagonal La2O3 films is located at 198 cm(-1), in good agreement with the first principles calculations, and at a lower frequency than the corresponding mode for cubic La2O3 is at 235 cm(-1). Accordingly, electrical measurements reveal a dielectric constant around 27 for hexagonal La2O3 films, significantly higher than the one around 17 derived for cubic La2O3 layers. (C) 2007 American Institute of Physics.

The evolution of HfO2(3-5 nm)/SiO2(0.5 nm)/Si(1 00) stacks during vacuum annealing was monitored in situ with the combination of X-ray photoelectron spectroscopy and low energy ion scattering techniques and supplemented with atomic force microscopy analysis to investigate the mechanism that triggers HfO2 degradation with Hf silicide formation. The reduction of SiO2 interfacial layer and the formation of local paths for SiO escape into vacuum are believed to be critical at vacuum annealing above T> 850 degrees C for the reaction between HfO2, and Si to start and eventually lead to the degradation of the former. (C) 2007 Elsevier Ltd. All rights reserved.