Copper-doped titanium oxynitride (TiN x O y ) thin films were grown by atomic layer deposition (ALD) using the TiCl4 precursor, NH3, and O2 at 420 °C. Forming gas was used to reduce the background ...oxygen concentration and to transfer the copper atoms in an ALD chamber prior to the growth initiation of Cu-doped TiN x O y . Such forming gas-mediated Cu-doping of TiN x O y films had a pronounced effect on their resistivity, which dropped from 484 ± 8 to 202 ± 4 μΩ cm, and also on the resistance temperature coefficient (TCR), which decreased from 1000 to 150 ppm °C–1. We explored physical mechanisms causing this reduction by performing comparative analysis of atomic force microscopy, X-ray photoemission spectroscopy, X-ray diffraction, optical spectra, low-temperature transport, and Hall measurement data for the samples grown with and without forming gas doping. The difference in the oxygen concentration between the films did not exceed 6%. Copper segregated to the TiN x O y surface where its concentration reached 0.72%, but its penetration depth was less than 10 nm. Pronounced effects of the copper doping by forming gas included the TiN x O y film crystallite average size decrease from 57–59 to 32–34 nm, considerably finer surface granularity, electron concentration increase from 2.2(3) × 1022 to 3.5(1) × 1022 cm–3, and the electron mobility improvement from 0.56(4) to 0.92(2) cm2 V–1 s–1. The DC resistivity versus temperature R(T) measurements from 4.2 to 300 K showed a Cu-induced phase transition from a disordered to semimetallic state. The resistivity of Cu-doped TiN x O y films decreased with the temperature increase at low temperatures and reached the minimum near T = 50 K revealing signatures of the quantum interference effects similar to 2D Cu thin films, and then, semimetallic behavior was observed at higher temperatures. In TiN x O y films grown without forming gas, the resistivity decreased with the temperature increase as R(T) = – 1.88T 0.6 + 604 μΩ cm with no semimetallic behavior observed. The medium range resistivity and low TCR of Cu-doped TiN x O y make this material an attractive choice for improved matching resistors in RF analog circuits and Si complementary metal–oxide–semiconductor integrated circuits.
We fabricated Cu-doped TiNxOy thin film resistors by using atomic layer deposition, optical lithography, dry etching, Ti/Cu/Ti/Au e-beam evaporation and lift-off processes. The results of the ...measurements of the resistance temperature dependence, non-linearity, S-parameters at 0.01–26 GHz and details of the breakdown mechanism under high-voltage stress are reported. The devices’ sheet resistance is 220 ± 8 Ω/□ (480 ± 20 µΩ*cm); intrinsic resistance temperature coefficient (TCR) is ~400 ppm/°C in the T-range of 10–300 K; and S-parameters versus frequency are flat up to 2 GHz with maximum variation of 10% at 26 GHz. The resistors can sustain power and current densities up to ~5 kW*cm−2 and ~2 MA*cm−2, above which they switch to high-resistance state with the sheet resistance equal to ~200 kΩ/□ (~0.4 Ω*cm) caused by nitrogen and copper desorption from TiNxOy film. The Cu/Ti/TiNxOy contact is prone to ageing due to gradual titanium oxidation while the TiNxOy resistor body is stable. The resistors have strong potential for applications in high-frequency integrated and hybrid circuits that require small-footprint, medium-range resistors of 0.05–10 kΩ, with small TCR and high-power handling capability.
A range of natural oils such as rapeseed, sunflower, corn, linseed, and mustard ones has been used for fatty acid ethyl esters synthesis. The last as pure biodiesel B
100
were mixed with fossil ...diesel B
0
to form blends B
20
, B
40
, B
60,
and B
80
. This study reports the effects of engine load and biodiesel percentage on the performance and emission of a tractor diesel engine fueled with biodiesel–diesel blends. It is stated that mixed fuels little inferior to mineral diesel in engine performance, but the observed reduction is not critical. The results showed that the engine performance (effective power and torque) depends primarily on the content of acids with C
18
carbon chain in the oil. It was also found that the highest performance among the blended fuels is introduced by ethyl esters of rapeseed oil, while corn and mustard oil ethyl esters presented the lowest emissions level. The emissions of rapeseed, sunflower, corn, linseed, and mustard ethyl esters are all lower than the base mineral fuel.
Xiongnu was a confederation of nomadic pastoral tribes (~200
bc
–100
ad
) that founded the first nomadic empire in Central Asia. According to archeological and historical data, the tribes played a ...key role in ethnic and cultural processes in Central Asia and adjacent regions of Eurasia. Genetic studies of the Xiongnu published to date have focused on remains from burial grounds in present-day Mongolia, in the southern part of the ancient Xiongnu area. However, paleoanthropological materials from numerous Xiongnu cemeteries and settlements in Transbaikalia (the southern region of Eastern Siberia, Russia) in the northern part of the Xiongnu Empire have not been examined genetically. Here, we analyzed mitochondrial DNA variation in a Transbaikalian Xiongnu population based on ancient DNA obtained from skeletal remains (
n
= 18) at four burial grounds to complement available Xiongnu genetic diversity data. We detected 16 mitochondrial DNA haplotypes belonging to seven East Eurasian haplogroups (A, B5, C, D4, G2a, N9a, and Y) in the Transbaikalian Xiongnu series. We observed substantial similarity between Transbaikalian and Mongolian Xiongnu series with respect to main haplogroup composition and frequencies. We observed several mitochondrial DNA clusters (N9a, Y, B5, and A16) and 11 of 16 haplotypes that were previously undetected in the Xiongnu gene pool. We also observed high similarity between the Xiongnu and contemporary indigenous populations of eastern Central Asia, particularly Mongolian-speaking groups. These findings extend our knowledge of Xiongnu genetic diversity.
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