Theresia Knobloch

TU Wien | TU Wien · Institute for Microelectronics

Two-dimensional materials promise excellent gate control and high drive currents at the ultimate scaling limit. However, numerous challenges must be overcome before silicon can potentially be replaced as the predominant channel material. For example, defects in two-dimensional materials and their vicinity pose a considerable challenge, as they have...

Defects play a pivotal role in limiting the performance and reliability of nanoscale devices. Field-effect transistors (FETs) based on atomically thin two-dimensional (2D) semiconductors such as monolayer MoS2 are no exception. Probing defect dynamics in 2D FETs is therefore of significant interest. Here, we present a comprehensive insight into var...

The operating characteristics of MOS transistors, such as the switching speed and power consumption, have been improved due to the increased reduction of the lateral dimensions. A further advantage of modern scaled nodes is that defects within the oxide and at the semiconductor/oxide interface are observed in a reduced number, however, they show an...

Charge trapping plays an important role for the reliability of electronic devices and manifests itself in various phenomena like bias temperature instability (BTI), random telegraph noise (RTN), hysteresis or trap-assisted tunneling (TAT). In this work we present Comphy v3.0, an open source physical framework for modeling these effects in a unified...

For ultra-scaled technology nodes at channel lengths below 12 nm, two-dimensional (2D) materials are a potential replacement for silicon since even atomically thin 2D semiconductors can maintain sizable mobilities and provide enhanced gate control in a stacked channel nanosheet transistor geometry. While theoretical projections and available experi...

Two-dimensional materials have been widely investigated to implement memristive devices for data storage or neuromorphic computing applications because of their ultra-scaled thicknesses and clean interfaces. For example, resistance switching in hexagonal boron nitride (h-BN) has been demonstrated. This mechanism is most of the time attributed to th...

One of the main drawbacks of the continuous scaling of MOS transistors is the increase in variability of the device characteristics, e.g. threshold voltage, SS, mobility, which represents a formidable challenge for robust electronic circuits. Device variability issues are categorized into contributions from time-zero threshold voltage variations, a...

Leakage currents through dielectrics in modern logic, memory, and power devices, and back-end interlevel layers can severely increase the time-zero power dissipation and shorten the lifetime of the material structure. Depending on thickness, material properties, and fabrication quality, different conduction mechanisms through the insulating layer,...

Electronic devices based on two-dimensional semiconductors suffer from limited electrical stability because charge carriers originating from the semiconductors interact with defects in the surrounding insulators. In field-effect transistors, the resulting trapped charges can lead to large hysteresis and device drifts, particularly when common amorp...

Within the last decade, considerable efforts have been devoted to the fabrication of transistors utilizing 2D semiconductors. Also, small circuits consisting of a few transistors have been demonstrated, including inverters, ring oscillators, and SRAM cells. However, for industrial applications, both time‐zero and time‐dependent variability in the p...

Inorganic molecular crystal films of antimony trioxide can be grown on 4-inch wafers via a thermal evaporation process and used as a top-gate oxide in two-dimensional molybdenum disulfide transistors.

Field-effect transistors based on two-dimensional (2D) materials have the potential to be used in very large-scale integration (VLSI) technology, but whether they can be used at the front end of line or at the back end of line through monolithic or heterogeneous integration remains to be determined. To achieve this, multiple challenges must be over...

Despite the breathtaking progress already achieved for electronic devices built from 2D materials, they are still far from exploiting their full theoretical performance potential. Many of these problems are due to the lack of suitable insulators which would go along with 2D materials as nicely as SiO 2 goes with Si. For instance, amorphous oxides k...

Despite the enormous progress achieved during the past decade, nanoelectronic devices based on two-dimensional (2D) semiconductors still suffer from a limited electrical stability. This limited stability has been shown to result from the interaction of charge carriers originating from the 2D semiconductors with defects in the surrounding insulating...

Complementary metal–oxide–semiconductor (CMOS) logic circuits at their ultimate scaling limits place extreme demands on the properties of all materials involved. The requirements for semiconductors are well explored and could possibly be satisfied by a number of layered two-dimensional (2D) materials, such as transition metal dichalcogenides or bla...

Complementary metal oxide semiconductor (CMOS) logic circuits at the ultimate scaling limit place the utmost demands on the properties of all materials involved. The requirements for semiconductors are well explored and could possibly be satisfied by a number of layered two-dimensional (2D) materials, like for example transition-metal dichalcogenid...

The two-dimensional semiconductor Bi2O2Se can be oxidized to create an atomically thin layer of Bi2SeO5 that can be used as the insulator in scaled field-effect transistors.

Mechanically exfoliated 2D hexagonal boron nitride (h‐BN) is currently the preferred dielectric material to interact with graphene and 2D transition metal dichalcogenides in nanoelectronic devices, as they form a clean van der Waals interface. However, h‐BN has a low dielectric constant (≈3.9), which in ultrascaled devices results in high leakage c...

Nanoelectronic devices based on 2D materials are far from delivering their full theoretical performance potential due to the lack of scalable insulators. Amorphous oxides that work well in silicon technology have ill-defined interfaces with 2D materials and numerous defects, while 2D hexagonal boron nitride does not meet required dielectric specifi...

Two-dimensional (2D) semiconductors are very promising for applications in next-generation field-effect transistors (FETs) which could overcome scaling limitations of Si technologies and thus extend the life of Moore’s law. The success at achieving this ambitious goal will depend on the availability of compatible insulators which are always require...

The continuous scaling of transistors has led to unprecedented challenges for interconnect technologies. Conventional barriers fail when thinned below 4 nm; therefore, novel materials and back‐end‐of‐line (BEOL) compatible synthesis are urgently needed. 2D transition metal dichalcogenides present a unique opportunity for addressing the scaling of i...

We propose double-gated n-type WSe2 FETs with low leakage, low hysteresis top gate high-k dielectric stack. The top gate dielectric layer is deposited by HfO2 ALD on an Al2O3 seed layer obtained from the evaporation and oxidation by air exposure of a 1.5 nm Al layer. When operated under back gate control, the fabricated WSe2 FETs behave as n-type e...

Two-dimensional semiconductors could be used to fabricate ultimately scaled field-effect transistors and more-than-Moore nanoelectronic devices. However, these targets cannot be reached without appropriate gate insulators that are scalable to the nanometre range. Typically used oxides such as SiO2, Al2O3 and HfO2 are, however, amorphous when scaled...

Two-dimensional (2D) semiconductors have been suggested both for ultimately-scaled field-effect transistors (FETs) and More-than-Moore nanoelectronics. However, these targets can not be reached without accompanying gate insulators which are scalable into the nanometer regime. Despite the considerable progress in the search for channel materials wit...

This paper investigates the potential of passivation coatings for surface acoustic wave devices (SAW) based on aluminum nitride as a piezoelectric layer to operate at temperatures up to 1000 °C and in pure oxygen atmosphere. To increase the durability of SAW devices, a thin passivation layer was deposited on top of the structure, consisting of eith...

MoS2 has received a lot of attention lately as a semiconducting channel material for electronic devices, in part due to its large band gap as compared to other 2D materials. Yet, the performance and reliability of these devices is still severely limited by defects which act as traps for charge carriers, causing severely reduced mobilities, hysteres...

Metal-oxide-semiconductor (MOS) devices are affected by generation, transformation, and charging of oxide and interface defects. Despite 50 years of research, the defect structures and the generation mechanisms are not fully understood. Most light has been shed onto the charging mechanisms of pre-existing oxide defects by using the non-radiative mu...

Even though the hysteresis in the gate transfer characteristics of two-dimensional (2D) transistors is a frequently encountered phenomenon, the physics behind it are up to now only barely understood, let alone modeled. Here we demonstrate that the hysteresis phenomenon can be captured accurately by a previously established non-radiative multiphonon...

Black phosphorus is considered a very promising semiconductor for two-dimensional field-effect transistors. Initially, the main disadvantage of this material was thought to be its poor air stability. However, recent studies have shown that this problem can be solved by suitable encapsulation. As such, long-term studies of the outstanding properties...

We report considerable improvement in the hysteresis and reliability of MoS2 field-effect transistors (FETs) introduced by chemical vapour deposition (CVD) of MoS2 and dielectric encapsulation. Our results show that a high-quality 15 nm thick Al2O3 layer allows for an efficient protection of the devices from adsorbent-type trapping sites. Combined...

Aluminum nitride (AlN) on sapphire has been investigated with two different pretreatments prior to sputter deposition of the AlN layer to improve the orientation and homogeneity of the thin film. An inverse sputter etching of the substrate in argon atmosphere results in an improvement of the uniformity of the alignment of the AlN grains and hence,...

Introduction MoS 2 is a next-generation 2D material which is considered for applications in digital electronics [1–3]. Although enormous progress has been made in the area of MoS 2 FETs, the available prototypes do not yet meet the high expectations. Commonly known reliability issues like the frequently observed hysteresis in the I D (V G ) charact...

The synthesis of piezoelectric two-dimensional (2D) materials is very attractive for implementing advanced energy harvesters and transducers, as these materials provide enormously large areas for the exploitation of the piezoelectric effect. Among all 2D materials, molybdenum disulfide (MoS2) has shown the largest piezoelectric activity. However, a...

The performance of MoS2 transistors is strongly affected by charge trapping in oxide traps with very broad distributions of time constants. These defects degrade the mobility and additionally lead to the hysteresis of the gate transfer characteristics, which presents a crucial performance and reliability issue for these new technologies. Here we pe...

We examine highly-stable black phosphorus field-effect transistors and demonstrate that they can exhibit reproducible characteristics for over ten months. Nevertheless, we show that the performance of these devices is affected by thermally activated charge trapping in oxide traps. In order to characterize these important traps, we introduce a unive...

The commonly observed hysteresis in the transfer characteristics of MoS2 transistors is typically associated with charge traps in the gate insulator. Since in Si technologies such traps can lead to severe reliability issues, we perform a combined study of both the hysteresis as well as the arguably most important reliability issue, the bias-tempera...

This paper investigates the performance of surface acoustic wave (SAW) devices consisting of reactively sputter deposited scandium doped aluminum nitride (ScxAl1-xN) thin films as piezoelectric layers on sapphire substrates for wireless sensor or for RF-MEMS applications. To investigate the influence of piezoelectric film thickness on the device...