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This article reports on the growth and density time dependence of electroless copper films deposited onto smooth gold surfaces as the fundamental background for studies of electroless copper morphology. Al/Au/Ti/Si͑100͒ substrates were immersed in an alkaline electroless copper bath ͑0.04 M CuSO 4 , 0.08 M ethylenediaminetetraacetic acid ͑EDTA͒, 0.004−0.24 M HCHO, 0.0004 M 2,2Ј-dipridyl͒ in order to obtain plated continuous films. Changing the HCHO concentration in the range of 0.04-0.24 M, both deposition rate and volumetric density rapidly increase followed by a slow increase tending to saturatation. Based on the mixed potential theory, a consistent explanation for this behavior is proposed.Nowadays, copper has been used for ultralarge scale integration ͑ULSI͒ metallization instead of aluminum due to its lower resistivity and higher resistance to electromigration. 1-6 As a consequence, much attention has been given to electrochemical processes, electrodeposition and electroless deposition, which yield better choices for ULSI interconnects when compared with alternatives such as chemical vapor deposition ͑CVD͒ and physical vapor deposition ͑PVD͒. 3 In addition, electrochemical deposition has the advantages of low tool cost, low process temperature, high quality material, and the ability to form alloys. 4 In particular, electroless deposition is an autocatalytic redox process in which metal ions are chemically reduced at catalytic surface substrates in the absence of any external current source. 5-10 A reducing agent supplies electrons to this surface and the complexed metal ions receive these electrons to be reduced to a zero state oxidation. Electroless Cu deposition in formaldehyde ͑HCHO͒ based plating bath with ethylenediaminetetraacetic acid ͑EDTA͒ as the complexing agent is generally expressed as the coupling of two partial electrochemical reactions as follows [2][3][4][11][12][13] In previous works, 11,13 the authors have studied the evolution of the surface morphology of electroless Cu films deposited in Cu-EDTA-HCHO chemical baths, having smooth catalytic Au as the initial surface. The influence of changing the HCHO concentration, pH, and temperature on the scaling exponents and on the average thickness growth rate was addressed. Also, high quality electroless copper films with polycrystalline structure and with low resistivity were obtained. 17 This letter reports on the growth and density-time-dependence of electroless copper films deposited onto smooth gold surfaces using a copper aqueous solution with formaldehyde as a reducing agent. ExperimentalThe samples used were Al ͑30 nm͒/Au ͑85 nm͒/Ti ͑30 nm͒, deposited by E-beam evaporation on Si͑100͒ with resistivity in the range of 1 to 10 ⍀ m and an area of 6.5 cm 2 . Before metal evaporation, silicon was carefully cleaned using the RCA

Titanium dioxide (TiO2) has been recognized as one of the most active photocatalysts for organic pollutant degradation under ultraviolet (UV) light irradiation. In order to reduce the fast charge recombination in the TiO2, various methods have been investigated, including the addition of metal oxide co-catalysts. Owing to the characteristic of the nanoparticles, the modification of nanoparticles involving heat treatment is still a challenging task. In this work, two commercial TiO2 nanoparticles, namely P25 and P90 (Evonik), were modified by copper oxides (CuO) and the photocatalytic activity was evaluated for degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) under UV light. The CuO/P25 and CuO/P90 samples with various loading amounts (0.1, 0.25, 0.5 and 1.0 wt %) were prepared by precipitation of copper(II) nitrate to the P25 or P90 nanoparticles at pH of 9, followed by calcination at 573 K. X-ray diffraction (XRD) patterns indicated that all samples have the characteristics of both anatase and rutile phases. While the addition of CuO did not much affect the structure, crystallite size, and anatase-rutile ratio of the P25 and P90 nanoparticles, the presence of the copper species was confirmed by the scanning electron microscopy (SEM) equipped with the energy-dispersive X-ray (EDX) spectroscopy. Moreover, fluorescence spectra also showed that the CuO quenched the emission intensity of both the P25 and P90 nanoparticles, suggesting the successful decrease of the charge recombination in the TiO2 nanoparticles. Photocatalytic activity tests showed that the P25 and P90 gave percentage degradation of 90 and 47 %, respectively, after a 1-hour reaction. Even though not much improvement was observed for P25 TiO2 nanoparticle after the CuO addition (92 %), the activity of P90 nanoparticle was enhanced from 47 % to 86–87 % with the CuO addition of 0.1–0.25 wt %. This study demonstrated that it is feasible to improve the photocatalytic activity of TiO2 commercial nanoparticles, in this case, the P90, by surface modification using the CuO.

Summary Background During orthodontic therapy, bond failure of molar tubes may delay treatment. With the high failure rate of molar tubes, alternative bonding techniques were tested to improve bond strength. Objectives To compare the failure rates of molar tubes bonded with conventional and alternative bonding techniques by adding a layer of compomer adhesive at the molar/tube interface. Trial design Single-centre, single-blinded, split-mouth, randomized clinical trial. Methods Patients aged 12 years or older, who required fixed appliance orthodontic treatment without extraction and with no occlusal interference were eligible to participate. They were allocated randomly using a simple non-stratified split-mouth design with a 1:1 allocation ratio. Blinding was only possible for the patients and data analysts. Molar tubes bonded with the modified bonding technique had an additional layer of compomer at the occlusal molar/tube interface. The patients were followed-up for nine months. Outcome measures included the survival time of molar tubes and the number of molar tubes debonded. The bond failure of molar tubes was analyzed using Kaplan–Meier and Cox regression analysis (P < 0.05). Results Thirty patients were recruited, randomized, and analyzed (mean age 20.33 years). The failure rate of molar tubes bonded with the modified bonding technique was 4.2 per cent and that of molar tubes bonded with the conventional bonding technique was 6.7 per cent. This difference was not statistically significant (P > 0.05). The dental arch and molar type were found to be as significant predictors for molar tube failure rate. No harm was detected during treatment. Limitations The effect of compomer to reduce enamel demineralization was not tested. Conclusions and implications The modified bonding technique did not significantly reduce the failure rate of molar tubes. The molar tubes bonded on the upper arch and second molars are more susceptible to debond. Registration The trial was registered with ClinicalTrials.gov on 21 May 2022 (Registration number: NCT05391386). Funding This research did not receive any funding.