In this study, ZnO thin films were deposited by atomic layer deposition (ALD) at various process temperatures. The purpose of this paper was to investigate the controllability of the preferred orientations of ZnO thin films by varying the process temperature and to determine the effect of the preferred orientations on the electrical properties of the films. The process temperature was varied from <mml:math display="inline"><mml:mrow><mml:mn>70</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mtext>to</mml:mtext><mml:mspace width="0.3em"></mml:mspace><mml:mn>250</mml:mn><mml:mo>°</mml:mo><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:math>70to250°C at several increments while the other ALD process parameters were fixed. The deposition rates and uniformities, crystal structures, and electrical properties of these films were evaluated at the various process temperatures. At process temperatures of 70 and <mml:math display="inline"><mml:mrow><mml:mn>90</mml:mn><mml:mo>°</mml:mo><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:math>90°C , ZnO thin films showed strong (002) preferred orientations with cylindrical, fine, columnar crystal structures, almost a 1:1 stoichiometric chemical ratio of Zn to O, and n-type carrier concentrations in the range of <mml:math display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mn>10</mml:mn></mml:mrow><mml:mrow><mml:mn>16</mml:mn></mml:mrow></mml:msup><mml:mspace width="0.3em"></mml:mspace><mml:msup><mml:mi>cm</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>1016cm−3 with resistivities of <mml:math display="inline"><mml:mrow><mml:mn>0.1</mml:mn><mml:mo>–</mml:mo><mml:mn>1</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>Ω</mml:mi><mml:mspace width="0.3em"></mml:mspace><mml:mi>cm</mml:mi></mml:mrow></mml:math>0.1–1Ωcm . ZnO thin films deposited at temperatures higher than <mml:math display="inline"><mml:mrow><mml:mn>110</mml:mn><mml:mo>°</mml:mo><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:math>110°C had wedge-shaped crystal structures, high oxygen deficiencies, and higher n-type carrier concentrations up to <mml:math display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mn>10</mml:mn></mml:mrow><mml:mrow><mml:mn>20</mml:mn></mml:mrow></mml:msup><mml:mspace width="0.3em"></mml:mspace><mml:msup><mml:mi>cm</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>1020cm−3 than the films deposited at lower temperatures.

We demonstrate the morphological control method of ZnO nanostructures by atomic layer deposition (ALD) on an Al₂O₃/ZnO seed layer surface and the application of a hierarchical ZnO nanostructure for a photodetector. Two layers of ZnO and Al₂O₃ prepared using ALD with different pH values in solution coexisted on the alloy film surface, leading to deactivation of the surface hydroxyl groups. This surface complex decreased the ZnO nucleation on the seed layer surface, and thereby effectively screened the inherent surface polarity of ZnO. As a result, a 2-D zinc hydroxyl compound nanosheet was produced. With increasing ALD cycles of ZnO in the seed layer, the nanostructure morphology changes from 2-D nanosheet to 1-D nanorod due to the recovery of the natural crystallinity and polarity of ZnO. The thin ALD ZnO seed layer conformally covers the complex nanosheet structure to produce a nanorod, then a 3-D, hierarchical ZnO nanostructure was synthesized using a combined hydrothermal and ALD method. During the deposition of the ALD ZnO seed layer, the zinc hydroxyl compound nanosheets underwent a self-annealing process at 150 °C, resulting in structural transformation to pure ZnO 3-D nanosheets without collapse of the intrinsic morphology. The investigation on band electronic properties of ZnO 2-D nanosheet and 3-D hierarchical structure revealed noticeable variations depending on the richness of Zn-OH in each morphology. The improved visible and ultraviolet photocurrent characteristics of a photodetector with the active region using 3-D hierarchical structure against those of 2-D nanosheet structure were achieved.

We report here that SnS₂ films deposited at 150 °C and annealed at below 350 °C have good potential for using 2D SnS₂ in flexible electronic devices.

Cobalt thin films were deposited by a remote plasma atomic layer deposition (ALD) system with a metalorganic precursor of dicobalt octacarbonyl <mml:math display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi>Co</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>(</mml:mo><mml:mi>CO</mml:mi><mml:msub><mml:mo>)</mml:mo><mml:mrow><mml:mn>8</mml:mn></mml:mrow></mml:msub><mml:mo>)</mml:mo></mml:mrow></mml:math>(Co2(CO)8) . To investigate the reaction kinetics and the characteristics of the Co films, we carried out experiments, varying parameters such as precursor flow rate and injection time, reactant gas flow rate, plasma power, and substrate temperature. The deposition rate of Co films was <mml:math display="inline"><mml:mrow><mml:mo>∼</mml:mo><mml:mn>1.2</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">Å</mml:mi><mml:mo>∕</mml:mo><mml:mi>cycle</mml:mi></mml:mrow></mml:math>∼1.2Å∕cycle in the ALD window of <mml:math display="inline"><mml:mrow><mml:mn>75</mml:mn><mml:mo>–</mml:mo><mml:mn>110</mml:mn><mml:mo>°</mml:mo><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:math>75–110°C . The extent of impurity content such as oxygen and carbon was highly affected by plasma power. Two Co films deposited with a plasma power of 50 and <mml:math display="inline"><mml:mrow><mml:mn>300</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">W</mml:mi></mml:mrow></mml:math>300W showed different compositional variations. The carbon content of the samples was about <mml:math display="inline"><mml:mrow><mml:mo>∼</mml:mo><mml:mn>22</mml:mn><mml:mo>%</mml:mo></mml:mrow></mml:math>∼22% and <mml:math display="inline"><mml:mrow><mml:mo>∼</mml:mo><mml:mn>15</mml:mn><mml:mo>%</mml:mo></mml:mrow></mml:math>∼15% , and oxygen content was about <mml:math display="inline"><mml:mrow><mml:mo>∼</mml:mo><mml:mn>15</mml:mn><mml:mo>%</mml:mo></mml:mrow></mml:math>∼15% and <mml:math display="inline"><mml:mrow><mml:mo>∼</mml:mo><mml:mn>2</mml:mn><mml:mo>%</mml:mo></mml:mrow></mml:math>∼2% , for deposition with plasma powers of 50 and <mml:math display="inline"><mml:mrow><mml:mn>300</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">W</mml:mi></mml:mrow></mml:math>300W , respectively. The incorporation of impurities was caused by the incomplete decomposition of <mml:math display="inline"><mml:mrow><mml:mi>Co</mml:mi><mml:mtext>-</mml:mtext><mml:mi>CO</mml:mi></mml:mrow></mml:math>Co-CO and suppressed Co reaction on Si substrate, retarding silicide formation.