Filed by Archimedes Tech SPAC Partners II Co.

pursuant to Rule 425 under the Securities Act of 1933

and deemed filed pursuant to Rule 14a-12

under the Securities Exchange Act of 1934

Subject Company: Archimedes Tech SPAC Partners II Co.

Commission File No. 001-42514

Date: April 22, 2026

SOCIAL MEDIA POSTS:

The following communication was first made by Archimedes Tech SPAC Partners II Co. (“ATII”) and certain of its officers and directors on April 22, 2026 via their social media accounts:

Archimedes Tech SPAC II is excited to announce a signed business combination agreement with Forge Nano—a company building breakthrough atomic layer deposition technology for next-generation semiconductors and domestically-produced defense batteries. Their platform is already leveraged across critical applications and supported by a $100M Department of Energy grant, alongside strong partners and policy tailwinds. Looking forward to continue working with this exceptional team as they scale.

For more information related to the announcement, please see our press release: https://www.globenewswire.com/news-release/2026/04/21/3278115/0/en/Forge-Nano-U-S-Advanced-Manufacturing-Leader-for-AI-Era-Chips-and-Defense-Batteries-to-List-on-NASDAQ-through-Merger-with-Archimedes-Tech-SPAC-Partners-II-Co.html

ABOUT FORGE NANO

Forge Nano, Inc. (“Forge Nano”) is a leading U.S. based semiconductor equipment and advanced materials company pioneering Atomic Layer Deposition (“ALD”) technology for AI-era chip manufacturing and defense battery applications via its platform technology, Atomic Armor™. Atomic Armor™ is a scalable, adaptable nano-scale coating system that strengthens America’s most critical systems – at the atomic level. The superior surface coatings produced by Forge Nano’s Atomic Armor™ process allows partners to unlock peak performance. Learn more at https://www.forgenano.com.

ABOUT ARCHIMEDES II

Archimedes Tech SPAC Partners II Co. (“ATII”) is a Cayman Islands exempted company led by Chairman Eric R. Ball and CEO Long Long and is comprised of technology investors, corporate finance veterans, engineers and SPAC specialists. ATII was formed as a special purpose acquisition company, or SPAC, for the purpose of effecting a merger with one or more businesses in the technology industry. ATII completed its $230 million IPO in February 2025, and its units, ordinary shares and warrants currently trade on the NASDAQ under the ticker symbols “ATIIU,” “ATII” and “ATIIW,” respectively. The team’s prior SPAC, Archimedes Tech SPAC Partners Co., successfully closed its merger with SoundHound AI, Inc. in April 2022.

IMPORTANT INFORMATION AND WHERE TO FIND IT

In connection with the proposed business combination, ATII and Forge Nano intend to file documents with the SEC, including a registration statement on Form S-4 (the “Registration Statement”), which will include a proxy statement/prospectus of ATII, relating to the proposed business combination. The Registration Statement will be mailed to ATII’s shareholders in connection with the proposed business combination. BEFORE MAKING ANY VOTING DECISION, INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE REGISTRATION STATEMENT AND ANY OTHER DOCUMENTS TO BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED BUSINESS COMBINATION OR INCORPORATED BY REFERENCE IN THE REGISTRATION STATEMENT WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED BUSINESS COMBINATION. Any vote in respect of resolutions to be proposed at ATII’s extraordinary general meeting to approve the proposed business combination or other responses in relation to the proposed transaction should be made only on the basis of the information contained in the Registration Statement. Investors and security holders may obtain free copies of these documents (when they are available) and other related documents filed with the SEC at the SEC’s website at www.sec.gov or by directing a request to: Archimedes Tech SPAC Partners II Co., 2093 Philadelphia Pike #1968, Claymont, DE 19703.

PARTICIPANTS IN THE SOLICITATION

Each of ATII, Forge Nano and their respective directors, executive officers and other members of management and employees, under SEC rules, may be deemed to be “participants” in the solicitation of proxies from shareholders of ATII in favor of the proposed business combination. Information about ATII’s directors and officers is set forth in ATII’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025, which was filed with the SEC on March 4, 2026 and ATII’s other filings with the SEC. Additional information concerning the interests of ATII’s participants in the solicitation, which may, in some cases, be different than those of ATII’s shareholders generally, will be set forth in the Registration Statement relating to the proposed business combination when it becomes available. These documents are available free of charge at the SEC’s web site at www.sec.gov.

NO OFFER OR SOLICITATION

This communication is for information purposes only and is not intended to and does not constitute, or form part of, an offer, invitation or the solicitation of an offer or invitation to purchase, otherwise acquire, subscribe for, sell or otherwise dispose of any securities, or the solicitation of any vote or approval in any jurisdiction, pursuant to the proposed business combination or otherwise, nor shall there be any sale, issuance or transfer of securities in any jurisdiction in contravention of applicable law. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act.

FORWARD LOOKING STATEMENTS

This communication includes forward-looking information about, among other topics, the proposed business combination. All statements, other than statements of present or historical fact included in this communication regarding the proposed business combination, ATII’s and Forge Nano’s ability to consummate the proposed business combination, the benefits of the proposed business combination and the combined company’s future financial performance, as well as the combined company’s strategy, future operations, estimated financial position, estimated revenues and losses, projected costs, prospects, plans and objectives of management are forward-looking statements. When used in this communication, the words “could,” “should,” “will,” “may,” “believe,” “anticipate,” “intend,” “estimate,” “expect,” “project,” the negative of such terms and other similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain such identifying words. These forward-looking statements are based on the current expectations and assumptions of ATII’s and Forge Nano’s management about future events and are based on currently available information as to the outcome and timing of future events. Except as otherwise required by applicable law, ATII and Forge Nano disclaim any duty to update any forward-looking statements, all of which are expressly qualified by the statements in this section, to reflect events or circumstances after the date of this communication.

ATII and Forge Nano caution you that these forward-looking statements are subject to numerous risks and uncertainties, most of which are difficult to predict and many of which are beyond the control of either ATII or Forge Nano. Risks and uncertainties include, among other things: (i) risks related to the occurrence of any event, change or other circumstances that could delay the business combination or give rise to the termination of the agreements related thereto; (ii) risks related to the outcome of any legal proceedings that may be instituted against ATII or Forge Nano following announcement of the transactions; (iii) risks related to the inability to complete the proposed business combination due to the failure to obtain approval of the shareholders of ATII and Forge Nano, or other conditions to closing in the definitive agreement for the business combination; (iv) the risk that the proposed business combination disrupts ATII’s or Forge Nano’s current plans and operations as a result of the announcement of the transactions; (v) risks related to Forge Nano’s ability to realize the anticipated benefits of the proposed business combination, which may be affected by, among other things, competition and the ability of Forge Nano to grow and manage growth profitably following the proposed business combination; (vi) risks related to costs related to the proposed business combination; (vii) risks related to changes in applicable laws or regulations; (viii) risks related to Forge Nano’s ability to successfully develop and deploy new technologies to address the needs of its customers, business, financial condition and results of operations; (ix) risks related to the effects of competition on Forge Nano’s business; (x) risks related to the availability and cost of the raw materials necessary for the production of Forge Nano’s products; (xi) risks related to Forge Nano’s ability to meet the specifications and requirements of its customers or adequately provide them with effective support and services; (xii) risks related to delays in the construction and operation of production facilities; (xiii) risks related to intellectual property infringement, data protection, and other losses; (xiv) risks related to the amount of redemption requests made by ATII’s public shareholders; (xv) risks related to Forge Nano’s ability to operate effectively as a public company, including its ability to implement controls and procedures required for public companies following the business combination; (xvi) risks related to changes in domestic and foreign business, market, financial, political and legal conditions; (xvii) risks related to the possibility that ATII or Forge Nano may be adversely affected by other economic, business, and/or competitive factors; and (xviii) other risks discussed in ATII’s Annual Report on Form 10-K and that will be presented in the Registration Statement, when available. There may be additional risks that ATII or Forge Nano presently do not know or that ATII or Forge Nano currently believe are immaterial that could also cause actual results to differ from those contained in the forward-looking statements. Should one or more of the risks or uncertainties described in this communication, or should underlying assumptions prove incorrect, actual results and plans could differ materially from those expressed or implied in any forward-looking statements. Additional information concerning these and other factors that may impact the operations and projections discussed herein can be found in ATII’s periodic filings with the SEC, including ATII’s Annual Report on Form 10-K and the Registration Statement, when available. ATII’s SEC filings are available free of charge on the SEC’s website at www.sec.gov.

You should carefully consider the foregoing factors and the other risks and uncertainties that affect the businesses of ATII and Forge Nano described in the “Risk Factors” and “Forward-Looking Statements” sections of the Registration Statement and other documents filed or to be filed by either of them from time to time with the SEC, all of which are available at www.sec.gov. These filings identify and address other important risks and uncertainties that could cause actual events and results to differ materially from those contained in the forward-looking statements. Forward-looking statements speak only as of the date they are made. Readers are cautioned not to put undue reliance on forward-looking statements, and ATII and Forge Nano assume no obligation to, and do not intend to, update or revise these forward-looking statements, whether as a result of new information, future events, or otherwise, unless required by law. Neither ATII nor Forge Nano gives any assurance that it will achieve its expectations.