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Manipulating Material Properties of Atomic Layer Deposited Oxide Thin Films by Electric Field: Experimental and Computational Design (ALDBIAS)

Synthesis and Phase Control

Manipulating Material Properties of Atomic Layer Deposited Oxide Thin Films by Electric Field: Experimental and Computational Design (ALDBIAS)

Prof. Dr. Marek Sierka
Otto Schott Institute for Material Research (OSIM)
Friedrich Schiller University Jena

Löbdergraben 32 07743 Jena
Tel: (+49) 3641 9 47930
Fax: (+49) 3641 9 47792

Dr. rer. nat. Adriana Szeghalmi
Institute of Applied Physics (IAP)
Friedrich Schiller University Jena

Albert-Einstein-Str. 15, D-07745 Jena
Tel: (+49) 3641 9 47859
Fax: (+49) 3641 9 47802

Proj.-Nr. SI 938/8-1Proj.-Nr. SZ 253/2-1

The ALDBIAS project follows both technological and fundamental scientific objectives. On the technological side, ALDBIAS targets the advancement of plasma-enhanced (PE) atomic layer deposition (ALD) by applying an electric field (BIAS) to tailor the material properties at an atomic level. The scientific objective of the project is the profound understanding of relationships between material properties and factors influencing PEALD synthesis of thin oxide films, both with and without bias. The working hypothesis of ALDBIAS is that electric field can influence properties of PEALD synthesized materials by two mechanisms:

(i) Depending on the bias, electric field may increase or lower energy transfer between plasma sheath and the surface due to acceleration or deceleration, respectively, of the bombarding ions.
(ii) Assuming partially ionic character of the material electric field creates an additional force Fi = qi E, on each atom in the oxide layer, where qi is the partial atomic charge and E the electric field strength.

Energetic ions bombarding the surface can influence most material properties like refractive index, stress, transmission, crystallinity, thin film density. Ion – surface interaction can lead to various effects which are augmented by an external electric field: adatom migration, atomic peening, surface implantation or subplantation, interdiffusion in nanolaminates and composite materials, desorption or re-sputtering. The correlation between the roughness of TiO2 PEALD thin films and the self-bias potential is presented in Fig. 1. and Fig. 2 shows SEM images if the coating grown without and with an external electric field.

Manipulating Material Properties

Manipulating Material Properties

Manipulating Material Properties

Figure 1. Self-bias and roughness versus oxygen gas flow/ corresponding chamber pressure.Figure 2. SEM image of TiO2 PEALD film grown at 100°C using 50 sccm O2 flow and 300 W plasma power and 0 V DC bias showing numerous anatase crystallites (left) and at +25 V bias showing amorphous material (right).