Dependence Of Surface Potential Research Articles

Dust particle surface potential in fusion plasma with supra-thermal electrons

By solving the current balance equations, the effect of the supra-thermal electrons on the surface potential of a negatively charged dust particle in a fusion plasma is studied based on the orbital motion limited theory. A non-Maxwellian plasma is modeled by employing a q-non-extensive velocity distribution, where a decreased q-parameter (q < 1) yields increased population of supra-thermal electrons. It is found that with the decrease in the q-parameter, the surface potentials of tungsten and carbon dust particles become more negative. When the ion temperature or ion flow velocity is increased, the dust surface potential changes non-monotonically, which is first decreasing and then increasing. For a small q-parameter, the non-monotonic variation is more pronounced and the minimum value of surface potential moves toward higher values of the ion temperature or ion flow velocity. Due to the dependence of the dust particle surface potential on the supra-thermal electrons, the increased proportion of supra-thermal electrons causes the increase in the ion drag force and the decrease in the dust particle lifetime. Here, lifetime refers to the time taken for the dust surface temperature to increase from its initial value to the sublimation temperature (for carbon) or the melting temperature (for tungsten). The decrease in lifetime caused by supra-thermal electrons is significant as the dust particle radius is increased.

Evolution of dielectric surface potential induced by electron beam radiation

<p indent=0mm>Spacecrafts operate in a complex space plasma environment and are constantly exposed to cosmic ray radiation. The charging and discharging phenomena that occur on the dielectric surfaces result in major reliability issues for the spacecraft’s normal operation. Secondary electron emission (SEE) caused due to electron radiation is the primary inducement of dielectric surface charging, and the SEE level severely affects the charging and discharging status. In this paper, to discover the dynamic evolution process of dielectric surface charging under the circumstances of electron beam irradiation, we have conducted a systematic study on the surface potential and SEE behaviors under various irradiation situations. First, we fitted the secondary electron yield (SEY) curves for three dielectric materials with high resistance, namely MgO, Al₂O₃, and ZnO, and extracted the two critical energies (<italic>E</italic>₁ and <italic>E</italic>₂, where the SEY value equals 1 for the first and second time, respectively), SEY peak values, and the corresponding primary electron energy of the SEY peak value from the three SEY curves. Then, for the situation of electron beam radiating dielectric materials, we developed a physical model and simulated the dynamic evolution processes of the dielectric surface potential. The radiation source is a pulsed electron beam, and some radiating conditions include the following: The intensity of the beam current is set as 1 × <sc>10⁻⁹ A,</sc> the diameter of the electron beam spot is 1 × <sc>10⁻⁸ m,</sc> the width of a single pulse is 0.9 × <sc>10⁻⁹ s,</sc> and the period duration of a single pulse is 1 × <sc>10⁻⁹ s.</sc> We calculated the charge accumulating amount after pulse radiation and the corresponding variation quantity of the surface potential based on these assumed radiation parameters and the ideal charging situation without charge leakage. We discovered the evolution regularities of the potential variation rate, potential level, and potential balanced duration for the three irradiated materials by calculating the transient surface potential. Furthermore, we have simulated the dependence of surface potential on the radiation energy (<italic>E</italic>_p) of the electron beam. Several conclusions are summarized by analyzing the simulation and calculation results. First, the SEE characteristics of dielectric materials, particularly the two critical energy values <italic>E</italic>₁ and <italic>E</italic>₂, are the two key factors that affect positive or negative charging, as well as the balanced duration and balanced surface potential level. Second, the negative balanced surface potential induced by low energy electrons (<italic>E</italic>_p><italic>E</italic>₂) is only a few tens of volts; the balanced time is a few hundred pulses, and the surface potential variation rate first increases and then decreases. Third, the negative balanced surface potential induced by the high energy electrons (<italic>E</italic>_p><italic>E</italic>₂) is relatively high and its magnitude can reach <sc>10000 V;</sc> moreover, the balanced duration is relatively long (about several tens of thousands pulse duration). Fourth, because the positive balanced surface potential induced by the middle energy electrons (<italic>E</italic>₁<<italic>E</italic>_p<<italic>E</italic>₂) is extremely low, and the balanced time is short (less than a few tens of seconds), the variation rate of the positive surface potential rapidly decreases. Fifth, the dielectric material with a higher <italic>E</italic>₂ value exhibits a lower negative balanced surface potential and a long balanced duration, and this property makes the dielectric material with a high <italic>E</italic>₂ value play a more significant role in the suppression of surface charging. In this paper, we have discussed in detail the dynamic evolution regularities of surface potential when the dielectric is irradiated by an electron beam, which is beneficial for further analysis about dielectric surface charging, discharging, and further research on the charging defense.

Oxidation kinetics of transition metals exposed to molecular and atomic oxygen

In this work we analyze the oxidation of 30 nm polycrystalline transition metals films (Hf, Ta, Mo and Ru) at low temperatures (298 K to 473 K) upon the exposure to two different species: molecular oxygen and atomic oxygen. Using in-situ spectroscopic ellipsometry and in-vacuum X-ray photoelectron spectroscopy, we verify the oxide growth kinetics and the final stoichiometry after each exposure condition for the four metals, and explore the particularities present in each oxide growth mechanics. The temperature-dependent analysis enabled to experimentally obtain the dissociation energy of molecular oxygen at polycrystalline O covered surfaces. By applying the principles of coupled currents and the Cabrera-Mott oxide growth mechanism, we extract values of the energy barrier for oxidation and the field formed in both oxygen molecule-metal and atom-metal interaction, exploring the differences between both exposure conditions. We demonstrate that in oxide growth at low temperatures two key points should be highlighted: (i) the strong dependence of surface potential on reactive oxygen coverage; (ii) the interrelation between exposure conditions and crystalline oxide formation. The obtained results and analysis contribute to the understanding of oxidation processes at low temperatures, advancing the knowledge required for the design and synthesis of thin metal and oxide films.

Equivalent Circuit Modeling of a Dual-Gate Graphene FET

This paper presents a simple and comprehensive model of a dual-gate graphene field effect transistor (FET). The quantum capacitance and surface potential dependence on the top-gate-to-source voltage were studied for monolayer and bilayer graphene channel by using equivalent circuit modeling. Additionally, the closed-form analytical equations for the drain current and drain-to-source voltage dependence on the drain current were investigated. The distribution of drain current with voltages in three regions (triode, unipolar saturation, and ambipolar) was plotted. The modeling results exhibited better output characteristics, transfer function, and transconductance behavior for GFET compared to FETs. The transconductance estimation as a function of gate voltage for different drain-to-source voltages depicted a proportional relationship; however, with the increase of gate voltage this value tended to decline. In the case of transit frequency response, a decrease in channel length resulted in an increase in transit frequency. The threshold voltage dependence on back-gate-source voltage for different dielectrics demonstrated an inverse relationship between the two. The analytical expressions and their implementation through graphical representation for a bilayer graphene channel will be extended to a multilayer channel in the future to improve the device performance.

Analytical Current–Voltage Model for Double-Gate a-IGZO TFTs With Symmetric Structure for Above Threshold

This article presents an analytical model to reproduce the ${I}-{V}$ characteristics of a double-gate (DG) amorphous indium–gallium–zinc oxide (a-IGZO) TFT with symmetric structure. This model for the above-threshold region is based on the gate voltage dependence of surface potential and potential at the center of the semiconductor layer, which are described by analytical expressions. Considering the densities of the free and localized carrier in the semiconductor, the total carrier density, which is equal to the effective carrier density, is calculated. The carrier mobility, calculated as the ratio between the free carrier and the effective carrier density, depends on the gate voltage as a power law with the power parameter $\gamma $ different from zero, as it is typically represented for the amorphous TFT. The drain current model has only 13 model parameters and was validated with six different simulated transistor structures, as well as with an experimental device. A good coincidence of the modeled characteristics with both the simulated and experimental devices was obtained.

Electrostatic charging of the sunlit hemisphere of the Moon under different plasma conditions

Accounting for the continuous interaction of the solar radiation, the development of electrostatic charge on the sunlit lunar regolith under extreme plasma conditions has been investigated—the ambient plasma around Moon corresponds to the plasma parameters associated with the solar wind, wake region, SEP events, and terrestrial magnetosphere. The photoemission of electrons from the lunar surface corresponding to the solar radiation spectrum, electron energy-dependent secondary electron emission and simultaneous collection of the ambient non-Maxwellian plasma electrons/ions have been considered the dominant charging mechanisms. The lunar surface potential has been derived using the dynamical balance of the photoemission and plasma accretion currents over its surface—the potential dependence of the charging currents has consistently been accounted for. In results, the lunar surface potential dependence on the plasma, surface, and radiation parameters have been parametrically derived. For the high temperature plasma composition, the sunlit locations over the lunar surface are predicted to acquire a negative potential. The outcome infers that depending on topography and location along with realistic plasma/surface parameters, the lunar surface may hold significant contrast in charging, and it may differ by the orders of magnitude. Such disparity in the surface charging may act as a source of the transport of charged dust and local atmospheric charge (ions/electrons) over the lunar regolith.

Modeling of carbon nanotube ISFETs with high‐κ gate dielectrics for biosensing applications

AbstractAn electrochemical model for two fabricated CNT‐ISFETs has been developed by considering all chemical and physical parameters of the device and then simulated in MATLAB environment. Model has been developed by studying on some aspects of carbon nanotube‐based ion sensitive field effect transistor (CNT‐ISFET) with two high‐κ dielectric materials (HfO2 and ZrO2) fabricated by chemical solution process at low temperature. DC experiments have been performed on pH of the solution to determine the dependence of surface potential, threshold voltage, and drain current. Sensitivities of the devices have also been determined experimentally and found to be 57.5 and 60 mV/pH compared with theoretical values of 56.6 and 58.6 mV/pH for HfO2 and ZrO2 CNT‐ISFETs, respectively in the pH range of 5 to 9. Time domain experiments have been performed to determine the memory effects of the devices. Experiments showed drift rate of 0.52 and 0.683 mV/h at pH 7 for HfO2 and ZrO2 as gate oxides, respectively. The hysteresis widths are found to be 5.88 and 5.26 mV in a pH loop of 7 → 9 → 7 → 5 → 7 for loop time of 60 minutes, respectively, for HfO2 and ZrO2 dielectrics. The simulated results of the developed model are compared with experimentally obtained data and found to be in good agreement.

Influence of organic material and sample parameters on the surface potential in Kelvin probe measurements

Scanning Kelvin probe is a method for material surface studies. It is used to determine the work function of metals. In the case of organic semiconductors, the measured surface potential is considered to be the Fermi level of the material which has been shown in some cases. But in most papers, the surface potential dependence on the metal electrode or film thickness was observed. Material properties and their influence on the measured surface potential and its relation to the Fermi level previously have not been systematically studied. In this work, the surface potential was measured for different materials—metal, organic dielectric material, and organic semiconductors. In most of the cases, the obtained surface potential was dependent on the metal electrode work function. This dependence decreased with the increase in electrical conductivity of the material. Several materials were chosen for studies where sample thickness was varied. Results showed that for most of the studied semiconductors the sample thickness of around 1.5–2 µm was required to obtain surface potential values which do not depend on the electrode work function.

Analytical modeling of asymmetric hetero-dielectric engineered dual-material DG-TFET

The present work aims to incorporate the benefits of asymmetric hetero-dielectric engineering into the already popular dual-material double-gate tunnel field-effect transistor. Here, Poisson's equation in 2D, incorporating appropriate boundary conditions, is solved to obtain the surface potential variation along the channel while considering Young's popular parabolic approximation technique. From the potential profile, the electric field is derived, and the drain current expression is then extracted analytically, integrating the band-to-band tunneling generation rate over the tunneling region using Kane's model. The dependence of surface potential, electric field, and tunneling current on the device parameters is analyzed by varying the biasing voltages, gate oxide thickness, body thickness, and gate metal work function, demonstrating agreement with TCAD simulation results. The performance of the device is compared with the earlier-reported structure of the dual-material gate hetero-dielectric TFET on the basis of channel potential, electric field, and drain current. The proposed device exhibits higher ON-state current, better ON---OFF current ratio, and suppressed short-channel effects. The results also demonstrate the superiority of the graded dielectric over the single-dielectric and hetero-dielectric double-gate TFET.

Вплив температури та іонної сили середовища на поверхневий потенціал еритроцитів людини

During freezing of cell suspensions the ionic strength of extracellular and, subsequently, intracellular media is responsible for the changes in membrane potential of cells. In this research we revealed the temperature and concentration dependencies of the surface potential of human erythrocytes during freezing of the cell suspension at the points corresponding to the values of temperature and 1:1 concentration of the electrolyte according to the phase diagram of a water-NaCl binary system. The concentrations of sodium ions on the surface of erythrocytes depending on concentration and temperature of the bulk solution were determined. It has been shown that the concentration of sodium ions on the surface of cells was 1.5 times higher than that in the bulk solution. The kink of surface potential temperature dependence for human erythrocytes for 0.15 and 0.3 M concentrations of 1:1 electrolyte within 8...12°C temperature range was of special interest. This temperature dependence feature of the surface potential calculated for the charged surface with a particular surface charge density from the purely physical considerations without taking into account the structure and composition of the surface could be one of the causes of rearrangements in membrane at these temperatures. Misbalance of electrostatic interactions on the surface of membrane outer monolayer appeared as a result of an increased concentration of counterions on the surface of cells and correspondingly the reduced surface potential might trigger the rearrangements and changes in relationships between membrane protein and lipid components.Probl Cryobiol Cryomed 2017; 27(1): 19–28Â

Electrical Study of Trapped Charges in Copper-Doped Zinc Oxide Films by Scanning Probe Microscopy for Nonvolatile Memory Applications.

Charge trapping properties of electrons and holes in copper-doped zinc oxide (ZnO:Cu) films have been studied by scanning probe microscopy. We investigated the surface potential dependence on the voltage and duration applied to the copper-doped ZnO films by Kelvin probe force microscopy. It is found that the Fermi Level of the 8 at.% Cu-doped ZnO films shifted by 0.53 eV comparing to undoped ZnO films. This shift indicates significant change in the electronic structure and energy balance in Cu-doped ZnO films. The Fermi Level (work function) of zinc oxide films can be tuned by Cu doping, which are important for developing this functional material. In addition, Kelvin probe force microscopy measurements demonstrate that the nature of contact at Pt-coated tip/ZnO:Cu interface is changed from Schottky contact to Ohmic contact by increasing sufficient amount of Cu ions. The charge trapping property of the ZnO films enhance greatly by Cu doping (~10 at.%). The improved stable bipolar charge trapping properties indicate that copper-doped ZnO films are promising for nonvolatile memory applications.

A Potential-Based Characterization of the Transfer Gate in CMOS Image Sensors

A method to characterize the transfer gate (TG)- related parameters in a 4 T pixel is presented. The method is based on the pinning voltage measurement, which is proposed by Tan et al. [1] Using this method, the TG ON and OFF surface potential can be characterized. Based on the TG ON potential characterization, and according to the MOSFET model, the TG channel doping and the oxide thickness can be extracted from the measurements. Based on the TG OFF potential characterization, the TG surface potential dependence on the TG design parameters and the pixel biasing condition are analyzed. Using this method, whether the device is suffering from the drain-introduced barrier lowering effect or the short channel effect can be easily determined.

Topological surface states and Fermi arcs of the noncentrosymmetric Weyl semimetals TaAs, TaP, NbAs, and NbP

Very recently the topological Weyl semimetal (WSM) state was predicted in the noncentrosymmetric compounds TaAs, TaP, NbAs, and NbP and soon led to photoemission and transport experiments to verify the presumed topological properties such as Fermi arcs (unclosed Fermi surfaces) and the chiral anomaly. In this work, we have performed fully \textit{ab initio} calculations of the surface band structures of these four WSM materials and revealed the Fermi arcs with spin-momentum-locked spin texture. On the (001) polar surface, the shape of the Fermi surface depends sensitively on the surface terminations (cations or anions), although they exhibit the same topology with arcs. The anion (P or As) terminated surfaces are found to fit recent photoemission measurements well. Such surface potential dependence indicates that the shape of the Fermi surface can be manipulated by depositing guest species (such as K atoms), as we demonstrate. On the polar surface of a WSM without inversion symmetry, Rashba-type spin polarization naturally exists in the surface states and leads to strong spin texture. By tracing the spin polarization of the Fermi surface, we can also distinguish Fermi arcs from trivial Fermi circles. The four compounds NbP, NbAs, TaP, and TaAs present an increasing amplitude of spin-orbit coupling (SOC) in the band structure. By comparing their surface states, we reveal the evolution of topological Fermi arcs from the spin-degenerate Fermi circle to spin-split arcs when the SOC increases from zero to a finite value. Our work will help us understand the complicated surface states of WSMs and allow us to manipulate them, especially for future spin-revolved photoemission and transport experiments.

Temperature dependence of frequency dispersion in III–V metal-oxide-semiconductor C-V and the capture/emission process of border traps

This paper presents a detailed investigation of the temperature dependence of frequency dispersion observed in capacitance-voltage (C-V) measurements of III-V metal-oxide-semiconductor (MOS) devices. The dispersion in the accumulation region of the capacitance data is found to change from 4%–9% (per decade frequency) to ∼0% when the temperature is reduced from 300 K to 4 K in a wide range of MOS capacitors with different gate dielectrics and III-V substrates. We show that such significant temperature dependence of C-V frequency dispersion cannot be due to the temperature dependence of channel electrostatics, i.e., carrier density and surface potential. We also show that the temperature dependence of frequency dispersion, and hence, the capture/emission process of border traps can be modeled by a combination of tunneling and a “temperature-activated” process described by a non-radiative multi-phonon model, instead of a widely believed single-step elastic tunneling process.

Quantitative Characterization of Near-Interface Oxide Traps in 4H-SiC MOS Capacitors by Transient Capacitance Measurements

1．Introduction The characteristics of SiC MOS devices are often suffered from the effects of near-interface oxide traps, however, the quantitative analysis method of those traps has not been established. In this study we propose a method to estimate their density by transient capacitance measurement. We assume the oxide trap model [1], in which carriers in semiconductors interact with the traps in oxide by tunneling, with a widely-spread response time of the traps, due to the variation of the tunneling distance between the interface and the traps. 2. Characterization method Transient response of capacitance (C-t) gives the information of trapping behaviors of the carriers in MOS capacitors [2-3], since the change of amount of trapped charges shifts the C-V curve. In this study we employed the MOS capacitors fabricated by thermal oxidation of n-type 4H-SiC. The gate bias on a capacitor was kept in accumulation state (Vg=Vtrap) for 100 sec to fill the traps, before a sudden shift to flatband state (Vg=Vmeas) to observe the C-t characteristics. Taking account of widely-spread response time of the traps due to their depth distribution in oxide, the time-dependent change of capacitance would be described by extended-Debye relaxation model [4] instead of a conventional relaxation with a single time constant, as |C(t)-Ceq|≈|DC0|exp (-(t/τeff)β), where Ceq is the capacitance in thermal equilibrium, β is the stretched exponential factor (0<β<1) of response time, τeff is the effective relaxation time of the group of traps with distributed response time, and DC0 is the total change of capacitance. C-t characteristics at 200K and 300K were fitted by the above equation to determine DC0, from which the amount of trapped charges in near-interface traps per area (Qox ) was estimated by assuming that the distance of the traps from the interface is significantly shorter than the film thickness. Note that low temperature slows down the de-trapping process by a few orders because of the change of the Fermi-Dirac distribution. Even though our measurement system detects only relatively slow response (≥0.1 s), low temperature measurement enables us to evaluate the traps locating very shallow region(~ a few ongstroms from the interface). 3. Results and Discussions The observed C-t characteristics were well-fitted by the extended-Debye relaxation model as desribed above. The lower temperature measurements resulted in larger DC0 which is indicating more traps exist in the region closer to the interface. By changing the Vtrap while unchanging the Vmeas, we can vary the width of energy region of the traps contributing to the C-t characteristics. From the SiC surface potential dependence of Qox, we can deduce the effective density of states (Dox ) of the near-interface traps. We employed two kinds of MOS capacitors with different interface state density (Dit ): ~1012 cm-2eV-1 and ~1011 cm-2eV-1 at 0.2 eV below conduction band edge. For the near-interface oxide traps in shallow region (measured at 200K), we could detect Dox of 3-4×1012 cm-2eV-1 for the higher Dit sample, but only ~5×1011 cm-2eV-1 for the lower Dit sample. These traps are estimated to locate at a few angstroms distance from the interface, taking account of the tunneling mass of electrons in SiO2. On the other hand, both of the two samples showed relatively less density of traps for the deep region (measured at 300K), in the order of 1011 cm-2eV-1. The location of the traps detected at 300K is estimated to be ~ 1 nm depth from the interface. These results indicates that the oxide trap density in shallow region is significantly sensitive to the preparation condition of SiC/SiO2 interface. 4. Conclusions The method to determine the near-interface oxide trap density in MOS capacitors from transient capacitance characteristics was proposed and demonstrated for 4H-SiC MOS capacitors, by taking account of the wide distribution of distance between the traps and the interface. The effective state density of the near-interface traps was estimated to be 1011 ~1012 cm-2eV-1 for shallow location from the interface but ~1011 cm-2eV-1 for deep location for our MOS capacitors. 5. Acknowledgement This work was partly supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), “Next-generation power electronics” (funding agency: NEDO), and by JSPS KAKENHI.

Phase Separation and Magnetoelectric Properties of Locally Induced States in Manganites

Phenomenon of phase separation with charge segregation is considered for low-doped manganites. The effects of giant dielectric permittivity and colossal magnetocapacitance due to phase separation accompanied by charged inhomogeneities are discussed. Long-range Coulomb interaction is responsible for the formation of inhomogeneous charged states and determines their characteristic length scales. Polar nanoscale areas are also formed at room temperature by applying electric field via the tip of scanning probe microscope to the surface of La0.9Sr0.1MnO3 and La0.89Sr0.11MnO3 single crystals. These results show the dependence of surface potential of induced area on the writing time, which is similar to that for ferroelectrics.

Variations in the electrical properties of silicon MOS structures with a nanodimensional silicon oxide under the effect of water vapors

The dependences of surface potential and the density of surface states of silicon MOS structures with nanoscale silicon oxide on the humidity of the surrounding gaseous medium were investigated. Based on the model of moisture sensitivity of such structures being in depletion modes and weak inversion, an analytical dependence of the surface potential on the humidity was received and the criteria of its linearity were determined. The validity of the analytical dependence was confirmed experimentally.

Bending rigidity of phosphatidylserine-containing lipid bilayers in acidic aqueous solutions

The elastic properties of anion lipid-containing bilayers were studied in aqueous solutions with fixed ionic strength at pH ≤5. Giant vesicles from stearoyl-oleoyl-phosphatidylcholine (SOPC) with various contents of dioleoyl-phosphatidylserine (DOPS) were obtained via electroformation and observed in phase contrast and fluorescence. Two structural phases were found to coexist in vesicle membranes. Thermal fluctuation spectroscopy of quasispherical vesicles with homogeneous liquid membranes was applied for the quantification of their bending rigidity. The white-noise contribution, significantly influencing the calculated value of the bending modulus, was taken into account in the analysis of the thermal shape fluctuations of vesicles. Electrokinetic measurements with SOPC/DOPS liposomes provided information about their surface potential dependence on pH and also as a function of the DOPS molar content in bilayers. The experimentally obtained values for the bending rigidity of SOPC bilayers containing various amounts of DOPS are reported and discussed in the light of the existing theory for the electrostatic contribution to the bending modulus of charged lipid membranes.

Electron Energy-Dependent Charging Effects of Multilayered Dielectric Materials

Measurements of the charge distribution in electron-bombarded, thin-film, and multilayer dielectric samples showed that charging of multilayered materials evolves with time and is highly dependent on incident energy; this is driven by electron penetration depth, electron emission, and material conductivity. Based on the net surface potential's dependence on beam current, electron range, electron emission, and conductivity, measurements of the surface potential, displacement current, and beam energy allow the charge distribution to be inferred. To take these measurements, a thin-film disordered SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> structure with a conductive middle layer was charged using 200-eV and 5-keV electron beams with regular 15-s pulses at 1-500 nA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Results show that there are two basic charging scenarios, which are consistent with simple charging models; these are analyzed using independent determinations of the material's electron range, yields, and conductivity. Large negative net surface potentials led to electrostatic breakdown and large visible arcs, which have been observed to lead to detrimental spacecraft charging effects.

Effect of cysteamine layer on the interaction between gold and ZrO 2 surfaces

The formation of cysteamine layer on gold surfaces may have an effect on the distribution of either gold particle adsorbed to the ZrO2 surface or vice versa with the adjustment of the electrostatic interactions. The atomic force microscope (AFM) was used to measure the surface forces between the zirconia surface and the cysteamine surface s as a function of the salt concentration and pH value. With the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the forces were quantitatively analyzed to acquire the surface potential and charge density of the surfaces for each salt concentration and each pH value. The surface potential and charge density dependence on the salt concentration was described with the law of mass action, and the pH dependence was explained with the ionizable groups on the surface.