Controlled molecular deposition of natural organic molecules such as nucleobases (NBs) into well-defined thin films represents progress toward exciting new nanomaterials. The strongly emerging atomic/molecular layer deposition (ALD/MLD) technique provides us with an elegant way to realize the depositions through gas phase with atomic/molecular level accuracy. In the resultant thin films the organic molecules are bound together not only with hydrogen bonds but also via metal cation linkers and are likely to exhibit novel properties. Here we demonstrate the ALD/MLD of such thin films with monovalent sodium, divalent barium, or trivalent lanthanum as the metal linker and uracil or adenine as the NB component. Our metal-NB thin films are homogeneous, smooth, and in the case of sodium and barium also crystalline showing intense photoluminescence. We discuss the impact of the size and charge of the metal cation on the growth and properties of the films.
We present a new low-temperature atomic layer deposition (ALD) process based on Mn2(CO)10 and ozone as precursors to fabricate crystalline α-Mn2O3 and Mn3O4 thin films; the phase composition is controlled by the deposition temperature such that the former phase forms in the range 60-100 °C and the latter in the range 120-160 °C. In both cases an appreciably high growth rate of ∼1.2 Å per cycle is achieved. The spinel-structured Mn3O4 thin films are shown to be ferrimagnetic with the transition temperature determined to be at ∼47 K.
Transition-metal phosphides (TMP) prepared by atomic layer deposition (ALD) are reported for the first time. Ultrathin Co-P films were deposited by using PH3 plasma as the phosphorus source and an extra H2 plasma step to remove excess P in the growing films. The optimized ALD process proceeded by self-limited layer-by-layer growth, and the deposited Co-P films were highly pure and smooth. The Co-P films deposited via ALD exhibited better electrochemical and photoelectrochemical hydrogen evolution reaction (HER) activities than similar Co-P films prepared by the traditional post-phosphorization method. Moreover, the deposition of ultrathin Co-P films on periodic trenches was demonstrated, which highlights the broad and promising potential application of this ALD process for a conformal coating of TMP films on complex three-dimensional (3D) architectures.
The metal–organic Cu(i) complex 1,3-diisopropyl-imidazolin-2-ylidene copper hexamethyl disilazide has been tested as a novel oxygen-free precursor for atomic layer deposition of Cu with molecular hydrogen.
We propose and evaluate the use of metallocene compounds as reducing agents for the chemical vapour deposition (and specifically atomic layer deposition, ALD) of the transition metal Cu from metalorganic precursors.
In order to assess the potential of porous Si as thermoelectric material we have performed thermal conductivity measurements in dependence of both temperature and average structure size. Investigations on samples with average structure sizes between 7 nm and 100 nm reveal a pronounced reduction in thermal conductivity which is encouraging for the future use of porous Si as thermoelectric material. The observed dependence on structure size and temperature can be explained in terms of a simple kinetic model based on the reduction of the effective phonon mean free path.
We report the atomic layer deposition (ALD) of high-quality crystalline thin films of the spinel-oxide system (Co1-xNix)3O4. These spinel oxides are ferrimagnetic p-type semiconductors, and promising material candidates for several applications ranging from photovoltaics and spintronics to thermoelectrics. The spinel phase is obtained for Ni contents exceeding the x = 0.33 limit for bulk samples. It is observed that the electrical resistivity decreases continuously with x while the magnetic moment increases up to x = 0.5. This is in contrast to bulk samples where a decrease of resistivity is not observed for x > 0.33 due to the formation of a rock-salt phase. From UV-VIS-NIR absorption measurements, a change from distinct absorption edges for the parent oxide Co3O4 to a continuous absorption band ranging deep into the near infrared for 0 < x ≤ 0.5 was observed. The conformal deposition of dense films on high-aspect-ratio patterns is demonstrated.
Layered cobalt oxides based on the hexagonal CoO2 layer, e.g., NaxCoO2 and [CoCa3O3]0.62CoO2 (or “Ca3Co4O9”), are promising thermoelectric materials. Here, the authors investigate the atomic layer deposition (ALD) of these materials in a thin-film form; this is not trivial, in particular, for the former compound, as both Na and Co are little challenged as components of ALD thin films. The authors employ diketonate precursors for all the metal constituents and ozone as the source of oxygen. In both cases, a postdeposition heat-treatment in O2 is applied to get crystalline coatings; the processes are found amazingly robust in terms of metal precursor pulsing ratios. A striking difference between the two processes is the resultant morphology: while the Ca3Co4O9 films grow highly homogeneous and smooth, the NaxCoO2 coatings exhibit a rather unique reproducible 10–20 μm scale channel-like island structure for all x values investigated. Finally, the authors characterized their ALD Ca3Co4O9 films for their chemical, structural, and physical property details not previously reported.
'/%3e%3cpath d='M200 752.362h200v300H200z' style='fill:%23fff;fill-opacity:1;stroke:none' transform='translate(0 -752.362)'/%3e%3cpath d='M400 752.362h200v300H400z' style='fill:%23ff883e;fill-opacity:1;stroke:none' transform='translate(0 -752.362)'/%3e%3c/svg%3e)
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
'%3e%3cg id='b'%3e%3cpath id='a' stroke='%23000' stroke-width='2' d='M-6-25H6m-12 3H6m-12 3H6'/%3e%3cuse xlink:href='%23a' y='44'/%3e%3c/g%3e%3cpath stroke='%23fff' d='M0 17v10'/%3e%3ccircle r='12' fill='%23cd2e3a'/%3e%3cpath fill='%230047a0' d='M0-12A6 6 0 0 0 0 0a6 6 0 0 1 0 12 12 12 0 0 1 0-24z'/%3e%3c/g%3e%3cg transform='rotate(-123.69)'%3e%3cuse xlink:href='%23b'/%3e%3cpath stroke='%23fff' d='M0-23.5v3M0 17v3.5m0 3v3'/%3e%3c/g%3e%3c/svg%3e)
