Very large phase shift of microwave signals in a 6 nm Hf x Zr 1− x O 2 ferroelectric at ±3 V

Physica Status Solidi (a)

Dinescu

Dragoman³

2019

Self Cite

The paper presents the state-of-the art of nanoelectronic devices based on 2D materials related to the cutting edge of Moore's law. Ballistic electron devices, ferroelectric, and atomically thin heterostructures are analyzed to show the benefits of 2D materials applications in nanoelectronics. It is shown that these new devices fulfill the basic requirements for further developments of new materials and circuits architectures envisaged beyond the Moore law. However, in many aspects, these new devices, concepts, as well as their implementations, are at the very beginning, so that the main obstacles to be overcome and the inherent difficulties to design and fabricate nanoelectronic devices based on single-atom-or few-atoms-thick materials are also presented.

Section: D Ferroelectrics and Their Applicationsmentioning

confidence: 95%

2D Materials Nanoelectronics: New Concepts, Fabrication, Characterization From Microwaves up to Optical Spectrum

Physica Status Solidi (a)

Dinescu

Dragoman³

2019

Self Cite

Section: Atomically Thin Ferroelectricsmentioning

confidence: 99%

HfO₂‐Based Ferroelectrics Applications in Nanoelectronics

Aldrigo

Physica Rapid Research Ltrs

et al. 2021

Self Cite

In memoriam of Prof. Dan Dascalu IntroductionHafnium oxide (HfO 2 ) is the dielectric commonly used in fieldeffect transistors (FETs) fabricated in complementary metal oxide semiconductor (CMOS) technologies and, as such, retrieved in any very large-scale integrated (VLSI) circuits. Examples of such circuits include microprocessors or complex analog integrated circuits found in daily applications, for instance, in computers, smartphones, laptops, or incorporated in cars, airplanes, or medical equipments. Since the discovery of HfO 2 as a dielectric for modern integrated circuits, increasing its permittivity was a leading research issue in itself because higher permittivity values allow decreasing the effective oxide thickness (EOT), and so the leakage current; this is especially important when billions of Si FETs are integrated on a single chip. The solution found to boost the permittivity of HfO 2 is represented by structural phase transformations. [1] HfO 2 has its lowest electrical permittivity (ε r % 18) in its stable phase, which is the monoclinic phase. Higher permittivity values, of ε r % 27 in the cubic phase and ε r % 70 in the tetragonal phase, are achieved, nonetheless, in phases that are stable only at very high temperatures, exceeding 1700 C. The decrease in these temperatures is possible, however, by HfO 2 doping. Thus, the cubic and the tetragonal phases were first obtained at lower temperatures via Y doping [1] and, respectively, Si doping, [2] whereas a stable HfO 2 tetragonal phase at nearly room temperature was observed by growing HfO 2 via atomic layer deposition (ALD) and doping it with ZrO 2 . [3,4] As described in the recent review, [5] the stabilization of these phases is determined by the concentration of dopants, the annealing temperature, and the growing methods.These initial investigations focused on increasing the permittivity of HfO 2 lead eventually to the discovery of the orthorhombic phase of HfO 2 , which was associated with HfO 2 ferroelectricity. [6,7] This phase is obtained under different growth conditions in the presence of dopants, including those mentioned earlier, and requires strict control of dopant concentration, temperature, and mechanical strain. The most used orthorhombic HfO 2 -based ferroelectric, named further as Hf ZrO, is doped with Zr and is usually grown at the wafer level, up to 300 mm, using ALD. It thus benefits from the state-of-the-art CMOS technology. More recently, using Zr-doping and pulsed laser deposition (PLD), another rhombohedral phase of HfO 2 was discovered to be also ferroelectric. [7] The rhombohedral or orthorhombic Hf ZrO are ferroelectrics with similar electric performances; the origin of stable ferroelectricity in both cases being due to the induced strain between the top and/or down substrates sandwiching Hf ZrO. [8] Doping or strain application modifies the atomic structure of a material and can induce a phase transition, in particular can induce ferroelectricity in HfO 2 . Similarly, HfO 2 can transform into a weak magnetic material [9...

“…HfO 2 doped with Zr) and some applications are already based on their properties, such as intense piezoelectric properties [4] and pyroelectric response [5]. We have recently shown theoretically that an extraordinary tunability can be obtained based on Hf x Zr 1 − x O 2 ferroelectrics [6] and we have demonstrated experimentally that phase shifters with phase shifts larger than 60° at 1 GHz and 13° at 10 GHz, at maximum applied DC voltages of ±3 V, are working with moderate losses [7]. We are continuing this research demonstrating that the phased array in Fig.…”

Section: Electromagnetic Design and Fabrication Of The Ferroelectric‐mentioning

confidence: 99%

“…We are continuing this research demonstrating that the phased array in Fig. 1 a is able to shift its main lobe with 25° for bias voltages of only ±1 V. The proposed antenna system has two interdigital phase shifters (modelling and dimensions as in [7]), one for each antenna (see Fig. 1 b , with design and fabrication details), and the two antennas are distanced at λ /2 for broadside radiation ( λ is the free‐space wavelength, whereas λ g is the guided wavelength).…”

Section: Electromagnetic Design and Fabrication Of The Ferroelectric‐mentioning

confidence: 99%

2.55 GHz miniaturised phased antenna array based on 7 nm‐thick Hf _x Zr ₁ ₋ _x O ₂ ferroelectrics

Modreanu²,

Povey

et al. 2018

Electron. lett.

A miniaturised phased array, suitable for a low-power wireless device and able to be fed from its battery, is experimentally demonstrated. The phase array consists in two gold patch antennas, phase shifters and additional circuitry, all integrated on Hf x Zr 1−x O 2 /high-resistivity silicon 4 inch wafer. The radiation beam at 2.55 GHz is steered with 25°when the 7 nm-thick ferroelectric is biased with ±1 V.