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SiO2-Fe2O3 mixture films and nanolaminates were grown by atomic layer deposition from iron trichloride, hexakis(ethylamino)disilane, and ozone at 300 °C. Orthorhombic ɛ-Fe2O3 was identified in Fe2O3 reference films and in Fe2O3 layers grown to certain thicknesses between amorphous SiO2 layers. SiO2-Fe2O3 films could be magnetized in external fields, exhibiting saturation and hysteresis in nonlinear magnetization-field curves. Electrical resistive switching, markedly dependent on the ratio of the component oxides, was also observed in films with proper composition. For relatively conductive films, application of small signal measurements allowed one to record memory maps with notable squareness and defined distinction between high and low conductance states. [ABSTRACT FROM AUTHOR]

Silicon nanocrystals prepared by continuous-wave laser annealing of a free-standing Si/SiO2 superlattice are studied for the first time by using methods of surface analysis (scanning electron microscopy and atomic force microscopy). The surface topology and composition are compared with transmission electron microscopy images that show a projection through the whole film, allowing us to discriminate silicon nanocrystals located near the film surface. These nanocrystals have an unusual pear-like shape with the thinner part sticking out of the laser-illuminated surface. The non-spherical shape of these nanocrystals is explained by eruption of silicon pressurized at the stage of crystallization from the melt phase. This hypothesis is supported by the micro-Raman spectra which show low stress near the surface features, in contrast to the neighbouring regions having high compressive stress. [ABSTRACT FROM AUTHOR]

Mixtures and nanolaminates of Al2O3 and TiO2 with different alumina to titania ratios were prepared by atomic layer deposition. The studies were aimed at electrical characterization of metal-insulator-semiconductor capacitors formed by combining an insulating oxide with large band gap (Al2O3) with an oxide with high dielectric permittivity (TiO2). In mixtures, the ratio of Al2O3 and TiO2 growth cycles varied from 10:2 to 5:5 with target layer thickness in the range of 6.2–8.8 nm. In Al2O3–TiO2–Al2O3 nanolaminates, the thicknesses of Al2O3 and TiO2 constituent layers were in the ranges of 3–6 and 2–15 nm, respectively. Appreciable step coverage on deep trenched substrates with high aspect ratio (1:40) was achieved with short pulse and purge times otherwise suited for the deposition of planar capacitors. The measurements confirmed the model calculations of leakage currents for laminates, mixtures, and pure Al2O3 films predicting the lowest leakage for pure Al2O3 films at all possible equivalent oxide thickness (EOT) values. Inclusion of TiO2 as an oxide of higher permittivity but lower band offsets on Si considerably increased the leakage. Currents in the films became strongly affected by chemical and structural defects induced by the deposition process. The as-deposited films possessed higher EOT values and lower breakdown fields, compared to the model predictions. Flatband voltage shifts and hysteresis width of capacitance-voltage curves were also affected by built-in defects. Postdeposition annealing somewhat improved the dielectric performance of the films deposited. [ABSTRACT FROM AUTHOR]

Electroluminescent ZnS:Mn thin films were deposited by the atomic layer deposition (ALD) technique. The deposition processes were based on ZnI2 or ZnCl2 as the Zn source and Mn(thd)3 (thd=2,2,6,6-tetramethyl-3,5-heptanedionato) as the Mn source. The ZnI2 process was found to have a wide temperature range between 300 and 490 °C where the growth rate was independent of the deposition temperature, which offers the possibility to select the deposition temperature according to the thermal stability of the dopant precursor without reducing growth of ZnS. The electro-optical measurements suggested that the amount of space charge was lower within the phosphors made with the iodide process, which resulted in higher efficiency of the “iodide” devices as compared to the “chloride” devices. Brightness and efficiency of the best iodide device after 64 h aging were 378 cd/m2 and 2.7 lm/W, respectively, measured at 60 Hz and at 40 V above threshold voltage. Conversely, brightness and efficiency of the best chloride device after 64 h aging were 355 cd/m2 and 1.6 lm/W, respectively. On the other hand, changes in the emission threshold voltages indicated that the chloride devices aged slower than the iodide devices. Though the samples were annealed later at high temperature, the deposition temperature was found to be a significant parameter affecting the grain size, luminance, and efficiency of the devices. Overall, the results of this study show that a relatively small change in the Zn precursor can have a clear impact on the electro-optical properties of the devices, and that a mixed halide/metalorganic ALD process can produce an electroluminescent device that ages relatively slowly. [ABSTRACT FROM AUTHOR]

In this study, the authors investigated third-order optical nonlinearity in polyimide/Ta2O5 nanolaminates deposited by atomic layer deposition. Third harmonic signal measurements were done with a multiphoton microscope at an excitation wavelength of 1.55 μm, laser pulse duration of 150 fs, and estimated pulse energy of 1.2 nJ. Third-order optical nonlinearity is an essential property in optical signal applications for telecommunication. Transparency at telecommunication wavelengths and a high refractive index are desired for a material. Polyimide is optically transparent, enabling light guidance through the material. The refractive index of the material can be fine-tuned by combining polyimide with a substantially higher refractive index material—in this case, Ta2O5. The layer thicknesses in nanolaminates were varied, and the third harmonic generation was compared to plain polyimide and Ta2O5 reference films. Third harmonic generation in the nanolaminates decreased slightly and refractive index increased with increasing Ta2O5 content. Normalized third-order nonlinear susceptibilities, χ(3), calculated for the nanolaminates were between the values of Ta2O5 and polyimide and increased with increasing polyimide content. [ABSTRACT FROM AUTHOR]

Tin oxide thin films were grown by atomic layer deposition (ALD) from bis[bis(trimethylsilyl) amino]tin(II) with ozone and water. The ALD growth rate of tin oxide films was examined with respect to substrate temperature, precursor doses, and number of ALD cycles. With ozone two ALD windows were observed, between 80 and 100 °C and between 125 and 200 °C. The films grown on soda lime glass and silicon substrates were uniform across the substrates. With the water process the growth rate at 100-250 °C was 0.05-0.18Å /cycle, and with the ozone process, the growth rate at 80-200 °C was 0.05-0.11Å/cycle. The films were further studied for composition and morphology. The films deposited with water showed crystallinity with the tetragonal SnO phase, and annealing in air increased the conductivity of the films while the SnO2 phase appeared. All the films deposited with ozone contained silicon as an impurity and were amorphous and nonconductive both as-deposited and after annealing. The films were further deposited in TiO2 nanotubes aiming to create a pn-junction which was studied by I-V measurements. The TiO2 nanostructure functioned also as a test structure for conformality of the processes. [ABSTRACT FROM AUTHOR]

Thin solid films consisting of ZrO2 and Ta2O5 were grown by atomic layer deposition at 300 °C. Ta2O5 films doped with ZrO2, TaZr2.75O8 ternary phase, or ZrO2 doped with Ta2O5 were grown to thickness and composition depending on the number and ratio of alternating ZrO2 and Ta2O5 deposition cycles. All the films grown exhibited resistive switching characteristics between TiN and Pt electrodes, expressed by repetitive current-voltage loops. The most reliable windows between high and low resistive states were observed in Ta2O5 films mixed with relatively low amounts of ZrO2, providing Zr to Ta cation ratio of 0.2. [ABSTRACT FROM AUTHOR]

As2S3 thin films were deposited on glass and silicon (100) substrates by atomic layer deposition from tris(dimethylamino)arsine [(CH3)2N)3As] and H2S. Amorphous films were deposited at an exceptionally low temperature of 50 °C. No film growth was observed at higher temperatures. The films were amorphous and contained H and C as the main impurities. The refractive index was 2.3 at 1.0 μm. The films were sensitive to air humidity, but their stability was significantly improved by a protective Al2O3 layer. [ABSTRACT FROM AUTHOR]

In total, five metal oxide and one metal plasma-enhanced atomic layer deposition (PEALD) processes were studied with respect to the conformality of the coatings. The study reveals that also high aspect ratio structures (up to 60:1) can be coated conformally with remote PEALD. Oxides could relatively easily be deposited into demanding 3D structures with rather short cycle times but not the silver metal. The key factor in achieving excellent conformality seems to be that sufficient radical density is required to overcome the loss of radicals by recombination. In the case of metals where hydrogen plasma is applied the recombination of hydrogen radicals causes major difficulties in obtaining perfect conformality. [ABSTRACT FROM AUTHOR]

Cross junctions of carbon nanotubes (CNTs) separated by thin oxide layers have been fabricated, in which the top CNT is used as a local gate to control the electron transport through the lower CNT. Coulomb oscillation was observed in the lower CNTs at low temperatures. The gating field from the upper CNTs is seen to modulate the band structure in the lower CNTs, producing double quantum dot systems. The ability to modulate the electronic structure of CNTs in such a way opens up many possibilities for future electronic and logical nanodevices. [ABSTRACT FROM AUTHOR]