ALD-grown Al2O3 Research Articles

Growth of high-density Ir nanocrystals by atomic layer deposition for nonvolatile nanocrystal memory applications

A careful investigation is made of the growth of Ir nanocrystals (NCs) on Al2O3 by atomic layer deposition (ALD), and a charge trapping memory device using ALD-grown Ir NCs as the charge trapping layer and ALD-grown Al2O3/HfO2 as the tunneling/blocking layers is fabricated. It is found that the ex situ nucleation of Ir NCs on ALD-grown Al2O3 is difficult, though in situ growth can produce pure metallic Ir NCs with a face-centered cubic crystalline phase directly on ALD-grown Al2O3 at the initial growth stage, which follows the nucleation incubation model. The growth of these metallic Ir NCs is attributed to the presence of a uniform coverage of reactive groups (hydroxyl or dimethylaluminum) on the as-deposited fresh ALD-grown Al2O3 surface, which greatly promotes the uniform nucleation of Ir. Electrical measurements of p-Si/Al2O3/Ir NCs/HfO2 memory cells exhibit a large memory window of 4.2 V at the sweeping gate voltage of ±10 V, and a ∼76% retention property after 104 s at 75 °C. Also, a stable memory window of ∼2 V is achieved during the first 105 program/erase cycles under a ±10 V/10 ms program/erase operation. In situ ALD-grown Ir NCs with the highest density of 0.6 × 1012/cm2 provide a potential approach to fabricate large-area high-density NCs for future ultrahigh-density nonvolatile NC memory applications.

Plasma-Enhanced Atomic Layer Deposition of AlN Epitaxial Thin Film for AlN/GaN Heterostructure TFTs

AlN/GaN heterostructures were realized by growing AlN thin film with low-thermal-budget (300 °C) plasma-enhanced atomic layer deposition (ALD) on a semi-insulating GaN-on-sapphire template. Thin-film transistors (TFTs) have been successfully fabricated using in situ ALD-grown Al2O3 as the gate dielectric. The proposed TFTs exhibit good gate control with a low subthreshold swing of ~ 85 mV/decade and a low-field mobility of ~ 27 cm2/(V·s). This mobility is one order of magnitude higher than that obtained in AlN/GaN heterostructures grown by magnetron sputtering. The enhanced device performance is attributed to a high-quality ALD-AlN/GaN interface obtained by in situ remote-plasma predeposition cleaning and the subsequent epitaxial growth of AlN thin film by plasma-enhanced ALD.

Aluminum oxide passivated radial junction sub-micrometre pillar array textured silicon solar cells

We report radial, p–n junction, sub-micrometre, pillar array textured solar cells, fabricated on an n-type Czochralski silicon wafer. Relatively simple processing schemes such as metal-assisted chemical etching and spin on dopant techniques were employed for the fabrication of the proposed solar cells. Atomic layer deposition (ALD) grown aluminum oxide (Al2O3) was employed as a surface passivation layer on the B-doped emitter surface. In spite of the fact that the sub-micrometre pillar array textured surface has a relatively high surface-to-volume ratio, we observed an open circuit voltage (VOC) and a short circuit current density (JSC) as high as 572 mV and 29.9 mA cm−2, respectively, which leads to a power conversion efficiency in excess of 11.30%, for the optimized structure of the solar cell described herein. Broadband omnidirectional antireflection effects along with the light trapping property of the sub-micrometre, pillar array textured surface and the excellent passivation quality of the ALD-grown Al2O3 on the B-doped emitter surface were responsible for the enhanced electrical performance of the proposed solar cells.

Barrier properties of Al2O3 and alucone coatings and nanolaminates on flexible biopolymer films

Thin atomic layer deposited (ALD) Al2O3 coatings are efficient barriers against gases and vapors. Al2O3 coatings are, however, brittle and straining them generates defects that impair barrier properties. Flexibility of ALD-grown Al2O3 coatings on biopolymer substrates can be improved by separating thinner Al2O3 layers with inorganic–organic alucone layers. The number and size of defects were smaller for these nanolaminates compared to the thick Al2O3 films after straining, and hence straining deteriorated the oxygen barrier properties less when applied to the laminates than when applied to the Al2O3 coatings.

ALD-Grown Al2O3 as a Diffusion Barrier for Stainless Steel Substrates for Flexible Cu(InGa)Se2 Solar Cells

Al2O3 layer deposited by atomic layer deposition was successfully used as a diffusion barrier and insulator for the stainless steel substrate of a Cu(InGa)Se2 thin film solar cell. The 100–300 nm-thick Al2O3 coating on stainless steel improved the surface smoothness and presented reliable resistance. More importantly, the diffusion of detrimental impurities, such as Fe and Ni, was significantly reduced during CuInSe2 deposition at the substrate temperature of 550°C.

Atomic Layer Deposited Lanthanum-(Zirconate/Aluminate) Based High-K Dielectric Stacks For Future CMOS-Technology

We present an atomic layer deposition (ALD)-process scheme that allows us to deposit ternary oxides such as LaxAlyOz and LaxZryOz at low process temperatures of 250 {degree sign}C. We combine these oxides with ALD-grown Al2O3 to fabricate various high-k dielectric stacks. By means of metal gate / high-k oxide / semiconductor capacitors we evaluate these materials regarding their electrical properties and thermodynamic stability on silicon and germanium substrates. Concerning the silicon substrates, we observe that superior electrical characteristics are achieved if a thin layer of LaxZryOz is sandwiched between two about 1 nm thick Al2O3 layers. By this approach, hydroxylation of the La-containing oxides is suppressed, minimizing leakage currents as well as oxide- and interface charges.