[en] Amorphous alloys possess increased mechanical strength. Currently, the processing and shaping of amorphous alloys employ their superplasticity in the supercooled liquid phase, which has pushed research into the evolution behavior of the supercooled liquid area during the processing of amorphous alloys. In this study, a molecular dynamics technique was applied to analyze the development rules of the supercooled liquid area and the "shear transformation zone" during laser-assisted scratching of Cu${}_{50}$Zr${}_{50}$ amorphous alloy. It was discovered through research on temperature fluctuations that laser irradiation raises the temperature of the processing region, and the formation of the supercooled liquid region moves the characteristic point of material removal to an earlier stage. As the local temperature rises, the distribution of the supercooled liquid region changes from dispersed to an angle of about 30° with regard to the scratching direction, and the angle subsequently decreases. The variable laws of the "shear transformation zone" during the scratching process were explored based on the von Mises strain theory. The findings demonstrate that when laser energy rises, the Newtonian layer warms up and the "shear transformation zone" distribution angle gradually decreases. At 20 eV/ps, the angle between the "shear transformation zone" and the scratching direction achieves its smallest value of 33°, resulting in the largest overlap with the supercooled liquid region and the lowest content of the "shear transformation zone". By constructing a mathematical model for material removal efficiency, it was established that energy in the range of 20 eV/ps to 30 eV/ps demonstrates higher removal efficiency and a steady processing process while reducing surface roughness by 6-7%.

[en] High permittivity materials have been required to replace traditional SiO₂ as the gate dielectric to extend Moore's law. However, growth of a thin SiO₂-like interfacial layer (IL) is almost unavoidable during the deposition or subsequent high temperature annealing. This limits the scaling benefits of incorporating high-k dielectrics into transistors. In this work, a promising approach, in which an O-scavenging metal layer and a barrier layer preventing scavenged metal diffusing into the high-k gate dielectric are used to engineer the thickness of the IL, is reported. Using a Ti scavenging layer and TiN barrier layer on a HfO₂ dielectric, the effective removal of the IL and almost no Ti diffusing into the HfO₂ have been confirmed by high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. (semiconductor technology)

[en] As an emerging developing technique for next-generation lithography, directed self-assembly (DSA) of block copolymer (BCP) has attracted numerous attention and has been a potential alternative to supplement the intrinsic limitations of conventional photolithography. In this work, the self-assembling properties of a lamellar diblock copolymer poly(styrene-b-methylmethacrylate) (PS-b-PMMA, 22k-b-22k, L_0 = 25 nm) on Si substrate and an atomic layer deposition (ALD)-assisted pattern transfer technology for the application of DSA beyond 16/14 nm complementary metal oxide semiconductor (CMOS) technology nodes, were investigated. Firstly, two key processing parameters of DSA, i.e. annealing temperatures and durations of BCP films, were optimized to achieve low defect density and high productivity. After phase separation of BCP films, self-assembling patterns of low defect density should be transferred to the substrate. However, due to the nano-scale thickness and the weak resistance of BCP films to dry etching, it is nearly impossible to transfer the BCP patterns directly to the substrate. Therefore, an ALD-based technology was explored in this work, in which deposited Al_2O_3 selectively reacts with PMMA blocks thus hardening the PMMA patterns. After removing PS blocks by plasma etching, hardened PMMA patterns were left and transferred to underneath SiO_2 hard mask layer. Using this patterned hard mask, nanowire array of 25 nm pitch were realized on Si substrate. From this work, a high-throughput DSA baseline flow and related ALD-assisted pattern transfer technique were developed and proved to have good capability with the mainstream CMOS technology. - Highlights: • Optimization on self-assembly process for high productivity and low defectivity • Enhancement of etching ratio and resistance by atomic layer deposition (ALD) • A hard mask was used for pattern quality improvement and contamination control.

[en] The effect of Si (100) surface S passivation was investigated. A thick film with a high roughness value was formed on the Si surface treated by (NH₄)₂S solution, which was attributed to physical adsorption of S atoms. SEM and XPS analyses reveal that Si surface atoms were chemically bonded with S atoms after Si surface treatment in NH₄OH and (NH₄)₂S mixing solution. This induces a more ideal value for the Schottky barrier height compared with a diode treated only by HF solution, indicating that surface states originating from dangling bonds are passivated with S atoms. (semiconductor devices)

[en] Oxygen incorporation into ZnSe thin films in Ar/O₂ or O₂ ambient during radio-frequency sputtering was studied in this paper. With the increase of oxygen partial pressure ratio, the poor crystalline quality occurred in the films accompanying with a SeO₂ secondary phase. The values of optical band gap for the films increased after light oxygen doping, ranging from 2.65 to 2.88 eV, which indicates the formation of ZnSeO ternary compounds. The near-band edge emission was observed in all samples, i.e., electronic transitions from the valence band to the conduction band. Nevertheless, heavy incorporation of O in ZnSe thin films led to the formation of the thin films with wide energy band gap (∼5.61 eV) and high optical transmittance (∼90%). X-ray photoelectron spectroscopy spectra indicate that oxygen atoms ionized by plasma enhanced the formation of SeO₂ bonds with Se of ZnSe under the non-equilibrium conditions and many oxygen ions incorporated in the random sites, resulting in the formation of amorphous states. - Highlights: • Oxygen incorporation into ZnSe thin films in Ar/O₂ or O₂ ambient during radio-frequency sputtering was studied. • The formation of ZnSeO ternary compounds occurred after light oxygen doping. • The enhancement of bandgap for heavily oxygen incorporated ZnSe thin films is due to the amorphous SeO₂ formation.

[en] Copper has been introduced in CdTe solar cell manufacturing for a long time and is critical for achieving high performance devices. In this work, CuCl thin films were prepared by vacuum thermal deposition and then used as a buffer layer with a thermal annealing treatment for activation in the CdTe solar cells. The results indicate that Cu and Cl diffused into the CdTe absorber which was beneficial for doping and copassivation. The carrier density for CdTe solar cells in the vicinity of the pn junction was significantly improved from 6.1 × 10¹³ to 4.3 × 10¹⁴ cm⁻³_, and V_oc was increased by >70 mV. The cell with the CuCl thin films was more uniform and revealed higher photocurrent response than the reference cell. The results also indicate that the formation of ohmic back contacts to CdTe solar cells due to the presence of the Cu_xTe (Cu₇Te₄) thin films. An optimal device with open circuit voltage of ~820 mV, and fill factor of ~72% and efficiency reaching 16.69% was obtained by the control of the copper concentration and the thermal activation conditions of the CuCl buffer layer.

[en] Vanadium diselenide thin films were prepared by electron beam evaporation. The properties of vanadium diselenide thin films were investigated using X-ray diffraction, scanning electron microscope, transmission spectra, electrical and Hall measurements. To further investigate the application of vanadium diselenide thin films, device performance in CdTe solar cells with a vanadium diselenide layer was also studied. The results indicate that vanadium diselenide thin films had a stable hexagonal structure after annealing. The thin films were p-type semiconductor materials with the high work function and high carrier concentration. Vanadium diselenide thin films could form a good ohmic contact to CdTe solar cells. Thus, cell performance was greatly improved when introduced a vanadium diselenide buffer layer. - Highlights: • VSe₂ was prepared by electron beam evaporation. • VSe₂ was a p-type material with the high work function and high carrier concentration. • VSe₂ was used as a Cu-free buffer layer in CdTe solar cells. • Performance of CdTe solar cells was improved

[en] Graphical abstract: A novel hierarchical disordered/ordered bilayer ZnO nanostructured film in the length of 18 μm have been successfully synthesized on the FTO substrate; the hierarchical ZnO nanostructured film electrodes applied in DSSCs exhibit photoelectric conversion efficiency as high as 5.16%. Highlights: •A novel hierarchical ZnO structure film was fabricated on a FTO substrate. •Hierarchical ZnO film is applied as the electrodes for dye sensitized solar cells. •The film possess high specific surface area and fast electron transport effect. •The light-scattering effect of the hierarchical film is pronounced. •The energy conversion efficiency of hierarchical ZnO electrode reaches to 5.16%. -- Abstract: A novel hierarchical ZnO nanostructured film is synthesized via a chemical bath deposition (CBD) method followed by a treatment of thermal decomposition onto a fluorine-doped tin oxide (FTO) substrate. This hierarchical film is composed of disordered ZnO nanorods (NRs) (top layer) and ordered ZnO nanowires (NWs) (bottom layer). The products possess the following features such as high specific surface area, fast electron transport, and pronounced light-scattering effect, which are quite suitable for dye sensitized solar cells (DSSCs) applications. A light-to-electricity conversion efficiency of 5.16% is achieved when the hierarchical ZnO nanostructured film is used as the photoanode under 100 mW cm⁻² illumination. This efficiency is found to be much higher than that of the DSSCs with pure ordered ZnO NWs (1.45%) and disordered ZnO NRs (3.31%) photoanodes

[en] Silica (SiO₂) thin films with different refractive indexes as the anti-reflection coating for cadmium telluride (CdTe) solar cells were prepared by sol–gel method in this paper. In order to obtain the preparation process of SiO₂ films with suitable refractive index, the different hydrolysis processes relied on the acid-base environment as well as the ratio of reactants was studied, respectively. It mainly includes that (I) the gel growth model in hydrogen or hydroxide ion environment provided by hydrochloric and ammonia. (II) The ratio of solvent, precursor and catalyst under base catalysis. (III) The weight and amount of polyethylene glycol molecular which is an additive agent to increase the porosity of sol film under acid catalysis. Based on the results above, a monolayer SiO₂ coating with optimized refractive index was applied onto the glass substrate of CdTe solar cell, and the quantum efficiency has been enhanced at the band of 400–800 nm. After that, multilayer SiO₂ coatings with high–low refractive indexes were designed according to the Fresnel theory to achieve wider spectrum (390–870 nm) enhancement. The broadband anti-reflection coatings (BARCs) were deposited on CdTe solar cell. The results were not consistent with expectations, which required further study about process matching between BARCs and device manufacture.

[en] Phase transformation characteristic of nitrogen (N)-rich hafnium nitride HfN_x (x>1) by post rapid thermal annealing (PRTA) process was investigated. Insulating N-rich HfN_1.44 film was grown by DC sputtering and 1000degC, 1 min PRTA process was carried out on this sample. The resistivity of the HfN_1.44 film can be reduced from insulating characteristic to metallic level of 3.6 x 10³ μΩ·cm, possibility due to decomposition of N-rich HfN_x (x>1) into HfN. This evolution can be attributed to the thermal instability of N-rich HfN_x (x>1) at high temperature. This result indicates a potential application of PRTA process in synthesizing pure HfN metal gate electrode for hafnium-based high-κ metal-oxide-semiconductor (MOS) stacks. (author)